Fix same crashy assumption that I fixed in r20967 later on in normal theme mode.

chrome/browser/gtk/gtk_chrome_button.cc

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/gtk/gtk_chrome_button.h"
 
 #include "base/basictypes.h"
 #include "base/gfx/gtk_util.h"
 #include "chrome/browser/gtk/nine_box.h"
 
@@ skipping 99 matching lines @@
     NineBox* nine_box = NULL;
     if (paint_state == GTK_STATE_PRELIGHT)
       nine_box = g_nine_box_prelight;
     else if (paint_state == GTK_STATE_ACTIVE)
       nine_box = g_nine_box_active;
 
     // Only draw theme graphics if we have some.
     if (nine_box)
       nine_box->RenderToWidget(widget);
 
-    gtk_container_propagate_expose(GTK_CONTAINER(widget),
-                                   gtk_bin_get_child(GTK_BIN(widget)),
-                                   event);
+    // If we have a child widget, draw it.
+    if (gtk_bin_get_child(GTK_BIN(widget))) {
+      gtk_container_propagate_expose(GTK_CONTAINER(widget),
+                                     gtk_bin_get_child(GTK_BIN(widget)),
+                                     event);
+    }
   }
 
   return TRUE;  // Don't propagate, we are the default handler.
 }
 
 GtkWidget* gtk_chrome_button_new(void) {
   return GTK_WIDGET(g_object_new(GTK_TYPE_CHROME_BUTTON, NULL));
 }
 
 void gtk_chrome_button_set_paint_state(GtkChromeButton* button,
@@ skipping 16 matching lines @@
 }
 
 void gtk_chrome_button_set_use_gtk_rendering(GtkChromeButton* button,
                                              gboolean value) {
   g_return_if_fail(GTK_IS_CHROME_BUTTON(button));
   GtkChromeButtonPrivate *priv = GTK_CHROME_BUTTON_GET_PRIVATE(button);
   priv->use_gtk_rendering = value;
 }
 
 G_END_DECLS