Fix of variable layer height mode opening from ObjectList:

when the respective object info line was clicked, the variable
layer height mode was opened correctly, but closing it through
the toolbar deactivated most of the icons as if it was just opened.

src/slic3r/GUI/Plater.cpp

@@ -5250,7 +5250,7 @@ void Plater::convert_unit(ConversionType conv_type)
 void Plater::toggle_layers_editing(bool enable)
 {
     if (canvas3D()->is_layers_editing_enabled() != enable)
-        wxPostEvent(canvas3D()->get_wxglcanvas(), SimpleEvent(EVT_GLTOOLBAR_LAYERSEDITING));
+        canvas3D()->force_main_toolbar_left_action(canvas3D()->get_main_toolbar_item_id("layersediting"));
 }
 
 void Plater::cut(size_t obj_idx, size_t instance_idx, coordf_t z, ModelObjectCutAttributes attributes)