Bug 850446 - Fix NULL deref in StartOffThreadIonCompile(). r=bhackett

js/src/jsworkers.cpp

@@ -30,6 +30,7 @@ js::StartOffThreadIonCompile(JSContext *cx, ion::IonBuilder *builder)
         if (!rt->workerThreadState->init(rt)) {
             js_delete(rt->workerThreadState);
             rt->workerThreadState = NULL;
+            return false;
         }
     }
     WorkerThreadState &state = *cx->runtime->workerThreadState;