--- widget/src/gtk2/nsFilePicker.cpp	2010-04-06 11:06:08.000000000 -0400
+++ widget/src/gtk2/nsFilePicker.cpp.oden	2010-04-06 11:06:34.000000000 -0400
@@ -601,7 +601,7 @@ nsCString nsFilePicker::kdeMakeFilter( i
 static PRInt32 windowToXid( nsIWidget* widget )
     {
     GtkWindow *parent_widget = get_gtk_window_for_nsiwidget( widget );
-    GdkWindow* gdk_window = gtk_widget_get_window( gtk_widget_get_toplevel( GTK_WIDGET( parent_widget )));
+    GdkWindow* gdk_window = gtk_widget_get_toplevel( GTK_WIDGET( parent_widget ) ) ? gtk_widget_get_toplevel( GTK_WIDGET( parent_widget ))->window : NULL;
     return GDK_WINDOW_XID( gdk_window );
     }