Bug 1250784: Follow-up: Fix merge conflict in bookmarks API. r=me

MozReview-Commit-ID: 83I9WhoUZGj

--HG--
extra : rebase_source : ba869cf2940eb5c52697c4e1f145c3fadb909fd2

browser/components/extensions/ext-bookmarks.js

@@ -55,7 +55,7 @@ function getTree(rootGuid, onlyChildren) {
       // It seems like the array always just contains the root node.
       return [convert(root, null)];
     }
-  });
+  }).catch(e => Promise.reject({message: e.message}));
 }
 
 function convert(result) {