Removed grab_notify to avoid crashes

Same fix as in:
http://git.xfce.org/users/eric/xfce4-power-manager/commit/?h=gtk3&id=4329d2601a35ccd2a48a509d9027b3a5707b3e4b

panel-plugin/scalemenuitem.c

@@ -46,8 +46,6 @@ static gboolean scale_menu_item_motion_notify_event     (GtkWidget          *men
                                                          GdkEventMotion     *event);
 static gboolean scale_menu_item_grab_broken             (GtkWidget          *menuitem,
                                                          GdkEventGrabBroken *event);
-static void     scale_menu_item_grab_notify             (GtkWidget          *menuitem,
-                                                         gboolean            was_grabbed);
 static void     scale_menu_item_parent_set              (GtkWidget          *item,
                                                          GtkWidget          *previous_parent);
 static void     update_packing                          (ScaleMenuItem  *    self);
@@ -109,7 +107,6 @@ scale_menu_item_class_init (ScaleMenuItemClass *item_class)
   widget_class->button_release_event = scale_menu_item_button_release_event;
   widget_class->motion_notify_event  = scale_menu_item_motion_notify_event;
   widget_class->grab_broken_event    = scale_menu_item_grab_broken;
-  widget_class->grab_notify          = scale_menu_item_grab_notify;
   widget_class->parent_set           = scale_menu_item_parent_set;
 
 
@@ -344,21 +341,6 @@ scale_menu_item_motion_notify_event (GtkWidget      *menuitem,
   return TRUE;
 }
 
-static void
-scale_menu_item_grab_notify (GtkWidget *menuitem,
-                             gboolean   was_grabbed)
-{
-  ScaleMenuItemPrivate *priv;
-
-  TRACE("entering");
-
-  g_return_if_fail (IS_SCALE_MENU_ITEM (menuitem));
-
-  priv = GET_PRIVATE (menuitem);
-
-  GTK_WIDGET_GET_CLASS (priv->scale)->grab_notify (priv->scale, was_grabbed);
-}
-
 static gboolean
 scale_menu_item_grab_broken (GtkWidget          *menuitem,
                              GdkEventGrabBroken *event)