How to solve ERROR: TypeError: in keyword argument precompile_statements_file?

Hi,

When I try to push my app to heroku, I am getting following error when I try to push
ERROR: TypeError: in keyword argument precompile_statements_file, expected Union{String, Vector{String}}, got a value of type Nothing .

The project.toml file contains
[

deps]
CSV = "336ed68f-0bac-5ca0-87d4-7b16caf5d00b"
Chain = "8be319e6-bccf-4806-a6f7-6fae938471bc"
Dash = "1b08a953-4be3-4667-9a23-3db579824955"
DashCoreComponents = "1b08a953-4be3-4667-9a23-9da06441d987"
DashDaq = "1b08a953-4be3-4667-9a23-a540cca008f6"
DashHtmlComponents = "1b08a953-4be3-4667-9a23-24100242a84a"
DashTable = "1b08a953-4be3-4667-9a23-f0e2ba4deb9a"
DashUserGuideComponents = "1b08a953-4be3-4667-9a23-e667f8ac7b1d"
DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
HTTP = "cd3eb016-35fb-5094-929b-558a96fad6f3"
JSON3 = "0f8b85d8-7281-11e9-16c2-39a750bddbf1"
Match = "7eb4fadd-790c-5f42-8a69-bfa0b872bfbf"
Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
PlotlyBase = "a03496cd-edff-5a9b-9e67-9cda94a718b5"
Printf = "de0858da-6303-5e67-8744-51eddeeeb8d7"
RDatasets = "ce6b1742-4840-55fa-b093-852dadbb1d8b"
UrlDownload = "856ac37a-3032-4c1c-9122-f86d88358c8b"

[compat]
julia = "1.6"
The complete trace while pushing to heroku is as  below:
Enumerating objects: 5, done.
Counting objects: 100% (5/5), done.
Delta compression using up to 4 threads
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 289 bytes | 289.00 KiB/s, done.
Total 3 (delta 2), reused 0 (delta 0), pack-reused 0
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Building on the Heroku-20 stack
remote: -----> Using buildpack: https://github.com/mbauman/heroku-buildpack-julia.git
remote: -----> Julia app detected
remote:   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
remote:                                  Dload  Upload   Total   Spent    Left  Speed
remote: 100   623  100   623    0     0   6230      0 --:--:-- --:--:-- --:--:--  6230
remote: 100 11.5M  100 11.5M    0     0  36.3M      0 --:--:-- --:--:-- --:--:-- 36.3M
remote: -----> Installing julia 1.6.0 ....        - julia-1.6.0-linux-x86_64.tar.gz
remote:   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
remote:                                  Dload  Upload   Total   Spent    Left  Speed
remote:   0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
remote: 100  107M  100  107M    0     0  40.7M      0  0:00:02  0:00:02 --:--:-- 43.5M
remote: ./.apt/usr/bin:./julia/bin:/usr/local/bin:/usr/bin:/bin
remote: ./.apt/usr/lib/x86_64-linux-gnu:./julia/lib:./julia/lib/x86_64-linux-gnu:
remote: cmake version 3.16.3 CMake suite maintained and supported by Kitware (kitware.com/cmake).
remote: julia version 1.6.0
remote:  done
remote:   Installing known registries into `~/.julia`
remote:        Added registry `General` to `~/.julia/registries/General`
remote:    Resolving package versions...
remote:    Installed PackageCompiler ─ v1.2.6
remote:     Updating `~/.julia/environments/v1.6/Project.toml`
remote:   [9b87118b] + PackageCompiler v1.2.6
remote:     Updating `~/.julia/environments/v1.6/Manifest.toml`
remote:   [9b87118b] + PackageCompiler v1.2.6
remote:   [0dad84c5] + ArgTools
remote:   [56f22d72] + Artifacts
remote:   [2a0f44e3] + Base64
remote:   [ade2ca70] + Dates
remote:   [f43a241f] + Downloads
remote:   [b77e0a4c] + InteractiveUtils
remote:   [b27032c2] + LibCURL
remote:   [76f85450] + LibGit2
remote:   [8f399da3] + Libdl
remote:   [56ddb016] + Logging
remote:   [d6f4376e] + Markdown
remote:   [ca575930] + NetworkOptions
remote:   [44cfe95a] + Pkg
remote:   [de0858da] + Printf
remote:   [3fa0cd96] + REPL
remote:   [9a3f8284] + Random
remote:   [ea8e919c] + SHA
remote:   [9e88b42a] + Serialization
remote:   [6462fe0b] + Sockets
remote:   [fa267f1f] + TOML
remote:   [a4e569a6] + Tar
remote:   [cf7118a7] + UUIDs
remote:   [4ec0a83e] + Unicode
remote:   [deac9b47] + LibCURL_jll
remote:   [29816b5a] + LibSSH2_jll
remote:   [c8ffd9c3] + MbedTLS_jll
remote:   [14a3606d] + MozillaCACerts_jll
remote:   [83775a58] + Zlib_jll
remote:   [8e850ede] + nghttp2_jll
remote:   [3f19e933] + p7zip_jll
remote: Precompiling project...
remote:   ✓ MbedTLS_jll
remote:   ✓ Zlib_jll
remote:   ✓ LibSSH2_jll
remote:   ✓ PackageCompiler
remote: 4 dependencies successfully precompiled in 3 seconds
remote:   Activating environment at `/tmp/build_f56227bc/Project.toml`
remote:    Installed LaTeXStrings ──────────────── v1.2.1
remote:    Installed SortingAlgorithms ─────────── v1.0.1
remote:    Installed IniFile ───────────────────── v0.5.0
remote:    Installed SentinelArrays ────────────── v1.3.3
remote:    Installed Tables ────────────────────── v1.4.4
remote:    Installed OrderedCollections ────────── v1.4.1
remote:    Installed HTTP ──────────────────────── v0.9.12
remote:    Installed Crayons ───────────────────── v4.0.4
remote:    Installed Missings ──────────────────── v1.0.0
remote:    Installed PlotlyBase ────────────────── v0.5.4
remote:    Installed CategoricalArrays ─────────── v0.10.0
remote:    Installed StructTypes ───────────────── v1.7.2
remote:    Installed DataStructures ────────────── v0.18.9
remote:    Installed DashHtmlComponents ────────── v1.1.3
remote:    Installed InvertedIndices ───────────── v1.0.0
remote:    Installed ProgressMeter ─────────────── v1.7.1
remote:    Installed JLLWrappers ───────────────── v1.3.0
remote:    Installed DataValueInterfaces ───────── v1.0.0
remote:    Installed Formatting ────────────────── v0.4.2
remote:    Installed Compat ────────────────────── v3.31.0
remote:    Installed UrlDownload ───────────────── v1.0.0
remote:    Installed TimeZones ─────────────────── v1.5.6
remote:    Installed Preferences ───────────────── v1.2.2
remote:    Installed DataAPI ───────────────────── v1.7.0
remote:    Installed Requires ──────────────────── v1.1.3
remote:    Installed DataFrames ────────────────── v1.2.0
remote:    Installed FileIO ────────────────────── v1.10.1
remote:    Installed PooledArrays ──────────────── v1.2.1
remote:    Installed Match ─────────────────────── v1.1.0
remote:    Installed IteratorInterfaceExtensions ─ v1.0.0
remote:    Installed Parsers ───────────────────── v1.1.0
remote:    Installed CodecZlib ─────────────────── v0.7.0
remote:    Installed Dash ──────────────────────── v0.1.4
remote:    Installed MD5 ───────────────────────── v0.2.1
remote:    Installed DashBase ──────────────────── v0.1.0
remote:    Installed JSON ──────────────────────── v0.21.1
remote:    Installed Kaleido_jll ───────────────── v0.1.0+0
remote:    Installed CSV ───────────────────────── v0.8.5
remote:    Installed Mocking ───────────────────── v0.7.1
remote:    Installed URIs ──────────────────────── v1.3.0
remote:    Installed TranscodingStreams ────────── v0.9.5
remote:    Installed RecipesBase ───────────────── v1.1.1
remote:    Installed RData ─────────────────────── v0.8.3
remote:    Installed ExprTools ─────────────────── v0.1.6
remote:    Installed DashDaq ───────────────────── v0.5.0
remote:    Installed Chain ─────────────────────── v0.4.7
remote:    Installed Reexport ──────────────────── v1.1.0
remote:    Installed PrettyTables ──────────────── v1.1.0
remote:    Installed TableTraits ───────────────── v1.0.1
remote:    Installed JSON2 ─────────────────────── v0.3.2
remote:    Installed MbedTLS ───────────────────── v1.0.3
remote:    Installed DocStringExtensions ───────── v0.8.5
remote:    Installed JSON3 ─────────────────────── v1.8.2
remote:    Installed DashCoreComponents ────────── v1.16.0
remote:    Installed RDatasets ─────────────────── v0.7.5
remote:    Installed DashTable ─────────────────── v4.11.3
remote:     Building TimeZones → `~/.julia/scratchspaces/44cfe95a-1eb2-52ea-b672-e2afdf69b78f/81753f400872e5074768c9a77d4c44e70d409ef0/build.log`
remote: Precompiling project...
remote:   ✓ IteratorInterfaceExtensions
remote:   ✓ Requires
remote:   ✓ Formatting
remote:   ✓ DocStringExtensions
remote:   ✓ URIs
remote:   ✓ Crayons
remote:   ✓ Match
remote:   ✓ Reexport
remote:   ✓ StructTypes
remote:   ✓ IniFile
remote:   ✓ LaTeXStrings
remote:   ✓ DataValueInterfaces
remote:   ✓ Chain
remote:   ✓ Compat
remote:   ✓ OrderedCollections
remote:   ✓ TranscodingStreams
remote:   ✓ SentinelArrays
remote:   ✓ Preferences
remote:   ✓ InvertedIndices
remote:   ✓ DataAPI
remote:   ✓ ProgressMeter
remote:   ✓ MD5
remote:   ✓ TableTraits
remote:   ✓ MbedTLS
remote:   ✓ Parsers
remote:   ✓ CodecZlib
remote:   ✓ JLLWrappers
remote:   ✓ Missings
remote:   ✓ PooledArrays
remote:   ✓ FileIO
remote:   ✓ Tables
remote:   ✓ DataStructures
remote:   ✓ JSON
remote:   ✓ JSON2
remote:   ✓ JSON3
remote:   ✓ HTTP
remote:   ✓ Kaleido_jll
remote:   ✓ SortingAlgorithms
remote:   ✓ CategoricalArrays
remote:   ✓ DashBase
remote:   ✓ UrlDownload
remote:   ✓ PrettyTables
remote:   ✓ DashTable
remote:   ✓ PlotlyBase
remote:   ✓ DashCoreComponents
remote:   ✓ DashHtmlComponents
remote:   ✓ CSV
remote:   ✓ Dash
remote:   ✓ DashUserGuideComponents
remote:   ✓ DashDaq
remote:   ✓ DataFrames
remote:   ✓ RData
remote:   ✓ RDatasets
remote: 53 dependencies successfully precompiled in 83 seconds (7 already precompiled)
remote: Pkg.Types.ProjectInfo(nothing, nothing, nothing, false, Dict{String, Base.UUID}("CSV" => UUID("336ed68f-0bac-5ca0-87d4-7b16caf5d00b"), "DashTable" => UUID("1b08a953-4be3-4667-9a23-f0e2ba4deb9a"), "DashCoreComponents" => UUID("1b08a953-4be3-4667-9a23-9da06441d987"), "Pkg" => UUID("44cfe95a-1eb2-52ea-b672-e2afdf69b78f"), "Dash" => UUID("1b08a953-4be3-4667-9a23-3db579824955"), "JSON3" => UUID("0f8b85d8-7281-11e9-16c2-39a750bddbf1"), "HTTP" => UUID("cd3eb016-35fb-5094-929b-558a96fad6f3"), "PlotlyBase" => UUID("a03496cd-edff-5a9b-9e67-9cda94a718b5"), "Match" => UUID("7eb4fadd-790c-5f42-8a69-bfa0b872bfbf"), "UrlDownload" => UUID("856ac37a-3032-4c1c-9122-f86d88358c8b"), "DashHtmlComponents" => UUID("1b08a953-4be3-4667-9a23-24100242a84a"), "DashUserGuideComponents" => UUID("1b08a953-4be3-4667-9a23-e667f8ac7b1d"), "RDatasets" => UUID("ce6b1742-4840-55fa-b093-852dadbb1d8b"), "DashDaq" => UUID("1b08a953-4be3-4667-9a23-a540cca008f6"), "Chain" => UUID("8be319e6-bccf-4806-a6f7-6fae938471bc"), "DataFrames" => UUID("a93c6f00-e57d-5684-b7b6-d8193f3e46c0"), "Printf" => UUID("de0858da-6303-5e67-8744-51eddeeeb8d7")), "/tmp/build_f56227bc/Project.toml")
remote: 17-element Vector{Symbol}:
remote:  :CSV
remote:  :DashTable
remote:  :DashCoreComponents
remote:  :Pkg
remote:  :Dash
remote:  :JSON3
remote:  :HTTP
remote:  :PlotlyBase
remote:  :Match
remote:  :UrlDownload
remote:  :DashHtmlComponents
remote:  :DashUserGuideComponents
remote:  :RDatasets
remote:  :DashDaq
remote:  :Chain
remote:  :DataFrames
remote:  :Printf
remote: false
remote: ERROR: TypeError: in keyword argument precompile_statements_file, expected Union{String, Vector{String}}, got a value of type Nothing
remote: Stacktrace:
remote:  [1] top-level scope
remote:    @ none:0
remote: -----> Discovering process types
remote:        Procfile declares types -> web
remote:
remote: -----> Compressing...
remote:        Done: 313.8M
remote: -----> Launching...
remote:  !     Warning: Your slug size (313 MB) exceeds our soft limit (300 MB) which may affect boot time.
remote:        Released v24
remote:        https://dash-julia-docs-staging.herokuapp.com/ deployed to Heroku
remote:
remote: Verifying deploy... done.
To https://git.heroku.com/dash-julia-docs-staging.git
   167ec79..4637524  mf/doctest -> master

Can anyone help to solve TypeError?