Fixed "extruder" column editing for non-object/part items. It's suppressed now.

+ Try to fix the wrong last column width updating under OSX

src/slic3r/GUI/GUI_ObjectList.hpp

@@ -185,6 +185,10 @@ public:
     void last_volume_is_deleted(const int obj_idx);
     bool has_multi_part_objects();
     void update_settings_items();
+
+private:
+    void OnStartEditing(wxDataViewEvent &event);
+
 };