KeyError: key :alpha not found

[jeremiedb]

• Issue concerns both the most recent CairoMakie release (v0.13.1) and master
• Reproduced on both Windows and Ubuntu, and from fresh temp environment

The following MWE works fine with CairoMakie v0.13.0. It however errors on both v0.13.1 and master.
My initial guess is that it may be related to changes brought by: to #4721

MWE:

using CairoMakie
f = Figure()
ax = Axis(f[1, 1])
density!(randn(100); label="test")
Legend(f[1, 2], ax)

ERROR: KeyError: key :alpha not found
Stacktrace:
  [1] getindex
    @ .\dict.jl:498 [inlined]
  [2] getindex
    @ C:\Users\jerem\.julia\packages\MakieCore\sHgwT\src\attributes.jl:106 [inlined]
  [3] getindex(x::Plot{Makie.density, Tuple{Vector{Float64}}}, key::Symbol)
    @ MakieCore C:\Users\jerem\.julia\packages\MakieCore\sHgwT\src\attributes.jl:192
  [4] getproperty
    @ C:\Users\jerem\.julia\packages\MakieCore\sHgwT\src\attributes.jl:86 [inlined]
  [5] legendelements(plot::Plot{Makie.density, Tuple{Vector{Float64}}}, legend::Attributes)
    @ Makie C:\Users\jerem\.julia\packages\Makie\Q6F2P\src\makielayout\blocks\legend.jl:529
  [6] LegendEntry(label::String, content::Plot{Makie.density, Tuple{Vector{Float64}}}, legend::Attributes; kwargs::@Kwargs{})
    @ Makie C:\Users\jerem\.julia\packages\Makie\Q6F2P\src\makielayout\blocks\legend.jl:408
  [7] LegendEntry
    @ C:\Users\jerem\.julia\packages\Makie\Q6F2P\src\makielayout\blocks\legend.jl:393 [inlined]
  [8] #2206
    @ .\none:0 [inlined]
  [9] iterate
    @ .\generator.jl:47 [inlined]
 [10] collect(itr::Base.Generator{Base.Iterators.Zip{Tuple{Vector{Plot{Makie.density, Tuple{Vector{Float64}}}}, Vector{String}}}, Makie.var"#2206#2207"{Attributes}})
    @ Base .\array.jl:834
 [11] to_entry_group(legend_defaults::Attributes, contents::Vector{Plot{Makie.density, Tuple{Vector{Float64}}}}, labels::Vector{String}, title::Nothing)
    @ Makie C:\Users\jerem\.julia\packages\Makie\Q6F2P\src\makielayout\blocks\legend.jl:577
 [12] Legend(fig_or_scene::GridPosition, contents::Vector{Plot{Makie.density, Tuple{…}}}, labels::Vector{String}, title::Nothing; bbox::Nothing, kwargs::@Kwargs{})
    @ Makie C:\Users\jerem\.julia\packages\Makie\Q6F2P\src\makielayout\blocks\legend.jl:613
 [13] Legend(fig_or_scene::GridPosition, contents::Vector{Plot{Makie.density, Tuple{Vector{Float64}}}}, labels::Vector{String}, title::Nothing)
    @ Makie C:\Users\jerem\.julia\packages\Makie\Q6F2P\src\makielayout\blocks\legend.jl:605
 [14] Legend(fig_or_scene::GridPosition, axis::Axis, title::Nothing; merge::Bool, unique::Bool, kwargs::@Kwargs{})
    @ Makie C:\Users\jerem\.julia\packages\Makie\Q6F2P\src\makielayout\blocks\legend.jl:665
 [15] Legend
    @ C:\Users\jerem\.julia\packages\Makie\Q6F2P\src\makielayout\blocks\legend.jl:662 [inlined]
 [16] Legend(fig_or_scene::GridPosition, axis::Axis)
    @ Makie C:\Users\jerem\.julia\packages\Makie\Q6F2P\src\makielayout\blocks\legend.jl:662
 [17] top-level scope
    @ REPL[7]:1
Some type information was truncated. Use `show(err)` to see complete types.