Fix recent changes to visible bell code

* src/gtkutil.c (xg_create_scroll_bar):
(xg_create_horizontal_scroll_bar): Stop ensuring an X window
before the widget is realized.
(xg_update_scrollbar_pos):
(xg_update_horizontal_scrollbar_pos): Ensure such a window here
instead.

src/gtkutil.c

@@ -4431,10 +4431,6 @@ xg_create_scroll_bar (struct frame *f,
 
   wscroll = gtk_scrollbar_new (GTK_ORIENTATION_VERTICAL, GTK_ADJUSTMENT (vadj));
 
-#if !defined HAVE_PGTK && GTK_CHECK_VERSION (2, 18, 0)
-  eassert (gdk_window_ensure_native (gtk_widget_get_window (wscroll)));
-#endif
-
   xg_finish_scroll_bar_creation (f, wscroll, bar, scroll_callback,
                                  end_callback, scroll_bar_name);
   bar->horizontal = 0;
@@ -4467,10 +4463,6 @@ xg_create_horizontal_scroll_bar (struct frame *f,
 
   wscroll = gtk_scrollbar_new (GTK_ORIENTATION_HORIZONTAL, GTK_ADJUSTMENT (hadj));
 
-#if !defined HAVE_PGTK && GTK_CHECK_VERSION (2, 18, 0)
-  eassert (gdk_window_ensure_native (gtk_widget_get_window (wscroll)));
-#endif
-
   xg_finish_scroll_bar_creation (f, wscroll, bar, scroll_callback,
                                  end_callback, scroll_bar_name);
   bar->horizontal = 1;
@@ -4542,6 +4534,12 @@ xg_update_scrollbar_pos (struct frame *f,
           gtk_widget_show_all (wparent);
           gtk_widget_set_size_request (wscroll, width, height);
         }
+
+#if !defined HAVE_PGTK && GTK_CHECK_VERSION (2, 18, 0)
+	if (!gdk_window_ensure_native (gtk_widget_get_window (wscroll)))
+	  emacs_abort ();
+#endif
+
       if (oldx != -1 && oldw > 0 && oldh > 0)
         {
           /* Clear under old scroll bar position.  */
@@ -4595,7 +4593,6 @@ xg_update_horizontal_scrollbar_pos (struct frame *f,
 				    int width,
 				    int height)
 {
-
   GtkWidget *wscroll = xg_get_widget_from_map (scrollbar_id);
 
   if (wscroll)
@@ -4642,6 +4639,11 @@ xg_update_horizontal_scrollbar_pos (struct frame *f,
         pgtk_clear_area (f, oldx, oldy, oldw, oldh);
 #endif
 
+#if !defined HAVE_PGTK && GTK_CHECK_VERSION (2, 18, 0)
+	if (!gdk_window_ensure_native (gtk_widget_get_window (wscroll)))
+	  emacs_abort ();
+#endif
+
       /* GTK does not redraw until the main loop is entered again, but
          if there are no X events pending we will not enter it.  So we sync
          here to get some events.  */