Merge pull request #1565 from matrix-org/matthew/group-promise-npe

turn NPE on flair resolution errors into a logged error

src/stores/FlairStore.js

@@ -129,7 +129,11 @@ class FlairStore extends EventEmitter {
         }
         const updatedUserGroups = resp.users;
         usersInFlight.forEach((userId) => {
+            if (this._usersPending[userId]) {
                 this._usersPending[userId].resolve(updatedUserGroups[userId] || []);
+            } else {
+                console.error("Promise vanished for resolving groups for " + userId);
+            }
         });
     }