Bug 949004 - Check to see if lock is null before using it. r=qDot

--HG--
extra : rebase_source : 115a50601853376ae1a0548aad4d61f58e96c8d1

dom/system/gonk/AutoMounterSetting.cpp

@@ -191,7 +191,10 @@ public:
     NS_ENSURE_TRUE(settingsService, NS_ERROR_FAILURE);
     nsCOMPtr<nsISettingsServiceLock> lock;
     settingsService->CreateLock(getter_AddRefs(lock));
-    lock->Set(UMS_STATUS, INT_TO_JSVAL(mStatus), nullptr, nullptr);
+    // lock may be null if this gets called during shutdown.
+    if (lock) {
+      lock->Set(UMS_STATUS, INT_TO_JSVAL(mStatus), nullptr, nullptr);
+    }
     return NS_OK;
   }