Fix crash in PluginService if the keys are null. It's still unclear why this...

Fix crash in PluginService if the keys are null.  It's still unclear why this is happening now as opposed to before.  This change just fixes the crash in the meantime.

BUG=70317
Review URL: http://codereview.chromium.org/6313007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72083 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/plugin_service.cc

@@ -218,8 +218,10 @@ PluginService::~PluginService() {
   // Release the events since they're owned by RegKey, not WaitableEvent.
   hkcu_watcher_.StopWatching();
   hklm_watcher_.StopWatching();
-  hkcu_event_->Release();
-  hklm_event_->Release();
+  if (hkcu_event_.get())
+    hkcu_event_->Release();
+  if (hklm_event_.get())
+    hklm_event_->Release();
 #endif
 }