Don't crash if there are no visible lines in a polyline

plugins/SimulationView/SimulationView.py

@@ -499,11 +499,11 @@ class SimulationView(CuraView):
                 continue
 
             for layer_index in layer_data.getLayers():
-                if len(layer_data.getLayer(layer_index).polygons) <= 0:  # Empty layer.
-                    continue  # Skip for performance.
                 for polyline in layer_data.getLayer(layer_index).polygons:
                     is_visible = numpy.isin(polyline.types, visible_line_types)
                     visible_indices = numpy.where(is_visible)
+                    if visible_indices[0].size == 0:  # No items to take maximum or minimum of.
+                        continue
                     visible_feedrates = numpy.take(polyline.lineFeedrates, visible_indices)
                     visible_linewidths = numpy.take(polyline.lineWidths, visible_indices)
                     visible_thicknesses = numpy.take(polyline.lineThicknesses, visible_indices)