Bug 1731298: Explicitly check if the worker is running in Exec. r=dom-worker-reviewers,jesup

Differential Revision: https://phabricator.services.mozilla.com/D140302

dom/workers/remoteworkers/RemoteWorkerChild.cpp

@@ -936,13 +936,17 @@ class RemoteWorkerChild::SharedWorkerOp : public RemoteWorkerChild::Op {
 
     auto lock = aOwner->mState.Lock();
 
-    MOZ_ASSERT(lock->is<Running>() || IsTerminationOp());
-
     if (IsTerminationOp()) {
       aOwner->CloseWorkerOnMainThread(lock.ref());
       return;
     }
 
+    MOZ_ASSERT(lock->is<Running>());
+    if (!lock->is<Running>()) {
+      aOwner->ErrorPropagationDispatch(NS_ERROR_DOM_INVALID_STATE_ERR);
+      return;
+    }
+
     RefPtr<WorkerPrivate> workerPrivate = lock->as<Running>().mWorkerPrivate;
 
     MOZ_ASSERT(workerPrivate);