fix parsing of empty table and respective test

Author: hhaensel

src/StippleActiveTables.jl

@@ -26,6 +26,8 @@ mutable struct ActiveTable
     data::DataFrame
 end
 
+ActiveTable() = ActiveTable(DataFrame())
+
 register_normal_element("active__table", context = @__MODULE__)
 
 function activetable(data::Symbol, args...; kwargs...)
@@ -38,6 +40,7 @@ function Stipple.render(at::ActiveTable)
 end
 
 function Stipple.stipple_parse(::Type{ActiveTable}, v::Vector)
+    isempty(v) && return ActiveTable(DataFrame())
     ActiveTable(DataFrame(permutedims(reduce(hcat, v[2:end])), v[1]))
 end
 

test/runtests.jl

@@ -49,7 +49,7 @@ using Stipple
 
         # Test empty vector
         empty_at = Stipple.stipple_parse(ActiveTable, [])
-        @test empty_at == DataFrame
+        @test empty_at.data == DataFrame()
     end
 
     @testset "Round-trip conversion" begin