fix error on empty edge arguments

fixes #237

Author: hexaeder

src/recipes.jl

@@ -783,7 +783,7 @@ end
 
 function _expand_args(args::Union{AbstractVector, AbstractDict}, ranges)
     N_paths = length(ranges)
-    N_points = ranges[end][end]
+    N_points = N_paths > 0 ? ranges[end][end] : 0
     allstraight = N_paths*3 == N_points
     if args isa AbstractVector && length(args) != N_paths
         throw(ArgumentError("The length of the args vector $args does not match the number of edges!"))

test/runtests.jl

@@ -278,9 +278,12 @@ end
     @test ax isa LScene
 end
 
-@testset "test empty endge Blot" begin
+@testset "test empty edge plot" begin
     GraphMakie.edgeplot(GraphMakie.Line{Point{2, Float32}}[])
     GraphMakie.edgeplot(GraphMakie.AbstractPath{Point{2, Float32}}[])
+
+    # test empty edge color
+    graphplot(SimpleGraph(2); edge_color=Symbol[])
 end
 
 include("referencetests.jl")