Bug 1510569 - Ensure TabChild's IPC actor is not dead before sending OnContentBlockingEvent message to TabParent r=nika

Differential Revision: https://phabricator.services.mozilla.com/D24807

--HG--
extra : moz-landing-system : lando

dom/ipc/TabChild.cpp

@@ -3310,6 +3310,10 @@ NS_IMETHODIMP TabChild::OnSecurityChange(nsIWebProgress* aWebProgress,
 NS_IMETHODIMP TabChild::OnContentBlockingEvent(nsIWebProgress* aWebProgress,
                                                nsIRequest* aRequest,
                                                uint32_t aEvent) {
+  if (!IPCOpen()) {
+    return NS_OK;
+  }
+
   Maybe<WebProgressData> webProgressData;
   RequestData requestData;
   nsresult rv = PrepareProgressListenerData(aWebProgress, aRequest,