Fix crash caused by uninstalling extension IME.

chrome/browser/chromeos/input_method/ibus_engine_controller.cc

 // Copyright (c) 2012 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/chromeos/input_method/ibus_engine_controller.h"
 
 #if defined(HAVE_IBUS)
 #include <ibus.h>
 #endif
 
@@ skipping 868 matching lines @@
     } else {
       connection->second->engine_instances_.erase(chromeos_engine);
       if (connection->second->active_engine_ == chromeos_engine) {
         connection->second->active_engine_ = NULL;
       }
     }
     if (chromeos_engine->table) {
       g_object_unref(chromeos_engine->table);
       chromeos_engine->table = NULL;
     }
-    if (ibus_bus_is_connected(chromeos_engine->connection->ibus_)) {
-      // We can't call destroy function without ibus-daemon connection,
+    if (chromeos_engine->connection &&
+        ibus_bus_is_connected(chromeos_engine->connection->ibus_)) {
+      // Connection may be NULL since extension IME can be uninstalled before
+      // |OnDestroy| is called.
+      // We can't call |destroy| function without ibus-daemon connection,
       // otherwise browser goes into deadlock state.
       // TODO(nona): investigate the reason of dead-lock.
       IBUS_OBJECT_CLASS(ibus_chromeos_engine_parent_class)
          ->destroy(IBUS_OBJECT(chromeos_engine));
     }
   }
 
   IBusEngineController::Observer* observer_;
   IBusBus* ibus_;
   IBusChromeOSEngine* active_engine_;
@@ skipping 61 matching lines @@
 #else
   return NULL;
 #endif
 }
 
 IBusEngineController::~IBusEngineController() {
 }
 
 }  // namespace input_method
 }  // namespace chromeos