fix unintended filling of simple lines

src/backends/pgfplotsx.jl

@@ -235,8 +235,7 @@ function (pgfx_plot::PGFPlotsXPlot)(plt::Plot{PGFPlotsXBackend})
                        segment_opt = merge( segment_opt, pgfx_marker(opt, i) )
                    end
                    if st == :shape ||
-                       isfilledcontour(series) ||
-                       series[:ribbon] === nothing
+                       isfilledcontour(series)
                        segment_opt = merge( segment_opt, pgfx_fillstyle(opt, i) )
                    end
                    # add fillrange

test/test_pgfplotsx.jl

@@ -16,6 +16,9 @@ end
     Plots._update_plot_object(pgfx_plot)
     @test pgfx_plot.o.the_plot isa PGFPlotsX.TikzDocument
     @test pgfx_plot.series_list[1].plotattributes[:quiver] === nothing
+    axis = Plots.pgfx_axes(pgfx_plot.o)[1]
+    @test count( x-> x isa PGFPlotsX.Plot, axis.contents ) == 1
+    @test !haskey(axis.contents[1].options.dict, "fill")
 
     @testset "3D docs example" begin
         n = 100