Fixed scroll the Object List to selected item on OSX & GTK

+ fixed #1395 (maximum PresetComboBox's width limit on Ubuntu)

src/slic3r/GUI/GUI_ObjectList.hpp

@@ -108,8 +108,6 @@ class ObjectList : public wxDataViewCtrl
     bool        m_parts_changed = false;
     bool        m_part_settings_changed = false;
 
-    int         m_selected_row = 0;
-
 public:
     ObjectList(wxWindow* parent);
     ~ObjectList();