Bug 824224 - IndexedDB blobs crash with 'ABORT: NULL actor value passed to non-nullable param.' r=cjones.

--HG--
extra : transplant_source : %FC%7F%83%B1%BCW%40%90%19M%96%18y%19%7B%A0%DE%E51h

dom/indexedDB/IDBObjectStore.cpp

@@ -1501,7 +1501,10 @@ IDBObjectStore::ConvertBlobsToActors(
 
       BlobParent* actor =
         aContentParent->GetOrCreateActorForBlob(blob);
-      NS_ASSERTION(actor, "This should never fail without aborting!");
+      if (!actor) {
+        // This can only fail if the child has crashed.
+        return NS_ERROR_DOM_INDEXEDDB_UNKNOWN_ERR;
+      }
 
       aActors.AppendElement(actor);
     }