[update_engine] handle NULL returns from strdup

dbus_service.cc

 // Copyright (c) 2010 The Chromium OS 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 "update_engine/dbus_service.h"
 #include <string>
 #include "base/logging.h"
 #include "update_engine/marshal.glibmarshal.h"
 
 using std::string;
@@ skipping 59 matching lines @@
   string new_version_str;
 
   CHECK(self->update_attempter_->GetStatus(last_checked_time,
                                            progress,
                                            &current_op,
                                            &new_version_str,
                                            new_size));
 
   *current_operation = strdup(current_op.c_str());
   *new_version = strdup(new_version_str.c_str());
+  if (!(*current_operation && *new_version)) {
+    *error = NULL;
+    return FALSE;
+  }
   return TRUE;
 }
 
 gboolean update_engine_service_reboot_if_needed(UpdateEngineService* self,
                                                 GError **error) {
   if (!self->update_attempter_->RebootIfNeeded()) {
     *error = NULL;
     return FALSE;
   }
   return TRUE;
 }
 
 gboolean update_engine_service_emit_status_update(
     UpdateEngineService* self,
     gint64 last_checked_time,
     gdouble progress,
     const gchar* current_operation,
     const gchar* new_version,
     gint64 new_size) {
   g_signal_emit(self,
                 status_update_signal,
                 0,
                 last_checked_time,
                 progress,
                 current_operation,
                 new_version,
                 new_size);
   return TRUE;
 }