Run julia-actions/julia-buildpkg@v1 fails at Julia 1.3

Tooling Package Management
1

I’m trying to setup CI for my own package https://github.com/jaksle/StableDistributions.jl. I’m not experienced with this. Julia lts, pre, 1 are fine, but Julia 1.3 (minimal version for my package) fails with

Run julia-actions/julia-buildpkg@v1
Run echo "JULIA_PKG_SERVER_REGISTRY_PREFERENCE=${JULIA_PKG_SERVER_REGISTRY_PREFERENCE:-eager}" >> ${GITHUB_ENV}
Run if "false" == "false" && !isdir(DEPOT_PATH[1])
ERROR: LoadError: MethodError: no method matching get(::Pair{String,Any}, ::String, ::Nothing)
Closest candidates are:
  get(!Matched::Base.EnvDict, ::AbstractString, ::Any) at env.jl:80
  get(!Matched::REPL.Terminals.TTYTerminal, ::Any, ::Any) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/REPL/src/Terminals.jl:176
  get(!Matched::IdDict{K,V}, ::Any, ::Any) where {K, V} at abstractdict.jl:596
  ...
Stacktrace:
 [1] Dict{Base.UUID,Pkg.Types.PackageEntry}(::Dict{String,Any}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/Pkg/src/manifest.jl:122
 [2] #read_manifest#45(::String, ::typeof(Pkg.Types.read_manifest), ::IOStream) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/Pkg/src/manifest.jl:151
 [3] #read_manifest at ./none:0 [inlined]
 [4] #48 at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/Pkg/src/manifest.jl:155 [inlined]
 [5] #open#271(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(open), ::Pkg.Types.var"#48#49"{String}, ::String) at ./io.jl:298
 [6] open at ./io.jl:296 [inlined]
 [7] read_manifest at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/Pkg/src/manifest.jl:154 [inlined]
 [8] Pkg.Types.EnvCache(::Nothing) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/Pkg/src/Types.jl:357
 [9] EnvCache at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/Pkg/src/Types.jl:336 [inlined]
 [10] Pkg.Types.Context() at ./util.jl:722
 [11] #build#105 at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/Pkg/src/API.jl:638 [inlined]
 [12] #build at ./none:0 [inlined]
 [13] #build#102 at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.3/Pkg/src/API.jl:635 [inlined]
 [14] #build at ./none:0 [inlined]
 [15] (::Base.var"#50#51#53"{ExponentialBackOff,Nothing,typeof(Pkg.API.build)})(::Base.Iterators.Pairs{Symbol,Bool,Tuple{Symbol},NamedTuple{(:verbose,),Tuple{Bool}}}, ::Base.var"#50#52"{Base.var"#50#51#53"{ExponentialBackOff,Nothing,typeof(Pkg.API.build)}}) at ./error.jl:266
 [16] (::Base.var"#kw##50#52")(::NamedTuple{(:verbose,),Tuple{Bool}}, ::Base.var"#50#52"{Base.var"#50#51#53"{ExponentialBackOff,Nothing,typeof(Pkg.API.build)}}) at ./none:0
 [17] top-level scope at /home/runner/work/_temp/90ccf82f-35e4-40e5-9363-6b5e85e842a0:32
 [18] include at ./boot.jl:328 [inlined]
 [19] include_relative(::Module, ::String) at ./loading.jl:1105
 [20] include(::Module, ::String) at ./Base.jl:31
 [21] exec_options(::Base.JLOptions) at ./client.jl:287
 [22] _start() at ./client.jl:460
in expression starting at /home/runner/work/_temp/90ccf82f-35e4-40e5-9363-6b5e85e842a0:32
Error: Process completed with exit code 1.

Alas, I have no idea what any of this means. Could anyone help?