Fix warning

modules/video_output/x11/xcommon.c

@@ -1627,10 +1627,9 @@ static int CreateWindow( vout_thread_t *p_vout, x11_window_t *p_win )
 
     if( !p_vout->b_fullscreen )
     {
-        p_win->owner_window = (Window)
-            vout_RequestWindow( p_vout, &p_win->i_x, &p_win->i_y,
+        void *ptr = vout_RequestWindow( p_vout, &p_win->i_x, &p_win->i_y,
                                         &p_win->i_width, &p_win->i_height );
-
+        p_win->owner_window = (uintptr_t)ptr;
         xsize_hints.base_width  = xsize_hints.width = p_win->i_width;
         xsize_hints.base_height = xsize_hints.height = p_win->i_height;
         xsize_hints.flags       = PSize | PMinSize;