Bug 1644913 - Avoid exceptions if the storage actor is destroyed while processing a new window r=ochameau

Differential Revision: https://phabricator.services.mozilla.com/D79276

devtools/server/actors/storage.js

@@ -276,6 +276,11 @@ StorageActors.defaults = function(typeName, observationTopics) {
       const host = this.getHostName(window.location);
       if (host && !this.hostVsStores.has(host)) {
         await this.populateStoresForHost(host, window);
+        if (!this.storageActor) {
+          // The actor might be destroyed during populateStoresForHost.
+          return;
+        }
+
         const data = {};
         data[host] = this.getNamesForHost(host);
         this.storageActor.update("added", typeName, data);