Don't place NULL pointers in the GDK window array in GTKGetWindow().

This avoids an assert in GTKUpdateCursor() later on.

Backport of r60458 from trunk.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@63217 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/radiobox.cpp

@@ -653,7 +653,8 @@ GdkWindow *wxRadioBox::GTKGetWindow(wxArrayGdkWindows& windows) const
     {
         GtkWidget *button = GTK_WIDGET( node->GetData()->button );
 
-        windows.push_back(button->window);
+        if (button->window)
+            windows.push_back(button->window);
 
         node = node->GetNext();
     }