Cannot add or dev a specific package

Hi all,

I am trying to add a package in a private repository to a new project.
I get the error below.
I’ve had no trouble adding packages in the same repository to the same project.
I also can’t dev the package.

Any ideas?

(MyProject) pkg> dev /projects/repos/MyPackage.jl
 Resolving package versions...
ERROR: MethodError: Cannot `convert` an object of type Nothing to an object of type String
Closest candidates are:
  convert(::Type{T<:AbstractString}, ::T<:AbstractString) where T<:AbstractString at strings/basic.jl:208
  convert(::Type{T<:AbstractString}, ::AbstractString) where T<:AbstractString at strings/basic.jl:209
  convert(::Type{T}, ::T) where T at essentials.jl:167
Stacktrace:                          
 [1] setindex!(::Dict{Base.UUID,String}, ::Nothing, ::Base.UUID) at ./dict.jl:380
 [2] deps_graph(::Pkg.Types.Context, ::Dict{Base.UUID,String}, ::Dict{Base.UUID,Pkg.Types.VersionSpec}, ::Dict{Base.UUID,Pkg.Types.Fixed}) at /buildworker/wor
ker/package_linux64/build/usr/share/julia/stdlib/v1.2/Pkg/src/Operations.jl:424
 [3] resolve_versions!(::Pkg.Types.Context, ::Array{Pkg.Types.PackageSpec,1}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.2/Pkg/src
/Operations.jl:316    
 [4] #develop#103(::Bool, ::typeof(Pkg.Operations.develop), ::Pkg.Types.Context, ::Array{Pkg.Types.PackageSpec,1}, ::Array{Base.UUID,1}) at /buildworker/worke
r/package_linux64/build/usr/share/julia/stdlib/v1.2/Pkg/src/Operations.jl:982
 [5] (::getfield(Pkg.Operations, Symbol("#kw##develop")))(::NamedTuple{(:strict,),Tuple{Bool}}, ::typeof(Pkg.Operations.develop), ::Pkg.Types.Context, ::Array
{Pkg.Types.PackageSpec,1}, ::Array{Base.UUID,1}) at ./none:0
 [6] #develop#17(::Bool, ::Bool, ::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(Pkg.API.develop), ::Pkg.Types.Context, ::Arr
ay{Pkg.Types.PackageSpec,1}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.2/Pkg/src/API.jl:59
 [7] develop at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.2/Pkg/src/API.jl:39 [inlined]
 [8] do_develop!(::Dict{Symbol,Any}, ::Array{Pkg.Types.PackageSpec,1}, ::Dict{Symbol,Any}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib
/v1.2/Pkg/src/REPLMode.jl:499
 [9] #invokelatest#1(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(Base.invokelatest), ::Any, ::Any, ::Vararg{Any,N} where
N) at ./essentials.jl:790
 [10] invokelatest(::Any, ::Any, ::Vararg{Any,N} where N) at ./essentials.jl:789
 [11] do_cmd!(::Pkg.REPLMode.Command, ::REPL.LineEditREPL) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.2/Pkg/src/REPLMode.jl:403
 [12] #do_cmd#23(::Bool, ::typeof(Pkg.REPLMode.do_cmd), ::REPL.LineEditREPL, ::String) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.
2/Pkg/src/REPLMode.jl:382
 [13] do_cmd at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.2/Pkg/src/REPLMode.jl:378 [inlined]
 [14] (::getfield(Pkg.REPLMode, Symbol("##28#31")){REPL.LineEditREPL,REPL.LineEdit.Prompt})(::REPL.LineEdit.MIState, ::Base.GenericIOBuffer{Array{UInt8,1}}, :
:Bool) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.2/Pkg/src/REPLMode.jl:610
 [15] #invokelatest#1 at ./essentials.jl:790 [inlined]
 [16] invokelatest at ./essentials.jl:789 [inlined]
 [17] run_interface(::REPL.Terminals.TextTerminal, ::REPL.LineEdit.ModalInterface, ::REPL.LineEdit.MIState) at /buildworker/worker/package_linux64/build/usr/s
hare/julia/stdlib/v1.2/REPL/src/LineEdit.jl:2306
 [18] run_frontend(::REPL.LineEditREPL, ::REPL.REPLBackendRef) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.2/REPL/src/REPL.jl:1038
 [19] run_repl(::REPL.AbstractREPL, ::Any) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.2/REPL/src/REPL.jl:201
 [20] (::getfield(Base, Symbol("##737#739")){Bool,Bool,Bool,Bool})(::Module) at ./client.jl:390
 [21] #invokelatest#1 at ./essentials.jl:790 [inlined]
 [22] invokelatest at ./essentials.jl:789 [inlined]
 [23] run_main_repl(::Bool, ::Bool, ::Bool, ::Bool, ::Bool) at ./client.jl:374
 [24] exec_options(::Base.JLOptions) at ./client.jl:312
 [25] _start() at ./client.jl:464

What julia version is this under? (you can check with the VERSION variable)

v1.2.0