[gtk-mac-integration] Fix double-free crash if last menu item is a separator.

[John Ralls <jralls src gnome org>]

commit e72a3dd706e7bb527a27515230e1027331c75722
Author: John Ralls <jralls ceridwen us>
Date:   Fri Oct 11 12:12:52 2013 -0700

    Fix double-free crash if last menu item is a separator.

 src/cocoa_menu_item.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/src/cocoa_menu_item.c b/src/cocoa_menu_item.c
index 38dbe71..5d8b71b 100644
--- a/src/cocoa_menu_item.c
+++ b/src/cocoa_menu_item.c
@@ -692,14 +692,17 @@ cocoa_menu_item_add_submenu (GtkMenuShell *menu_shell,
       _GNSMenuItem *item = (_GNSMenuItem*)[cocoa_menu itemAtIndex: index];
       if ([item isSeparatorItem] &&
          (last_cocoa_item == nil || [last_cocoa_item isSeparatorItem]))
+       {
          [cocoa_menu removeItem: item];
+         continue;
+       }
       if (([item respondsToSelector: @selector (isMarked)]) && [item isMarked])
        [cocoa_menu removeItem: item];
       else if (![item isHidden])
        last_cocoa_item = item;
     }
   /* Finally make sure that the last item isn't a separator. */
-  if ([last_cocoa_item isSeparatorItem])
+  if (last_cocoa_item != nil && [last_cocoa_item isSeparatorItem])
     [cocoa_menu removeItem: last_cocoa_item];
 
   g_list_free (children);