Return null if TagOrderStore is loading

The view should decide the default state.

src/components/structures/TagPanel.js

@@ -58,7 +58,7 @@ const TagPanel = React.createClass({
                 return;
             }
 
-            const orderedTags = TagOrderStore.getOrderedTags();
+            const orderedTags = TagOrderStore.getOrderedTags() || [];
             const orderedGroupTags = orderedTags.filter((t) => t[0] === '+');
             Promise.all(orderedGroupTags.map(
                 (groupId) => FlairStore.getGroupProfileCached(this.context.matrixClient, groupId),

src/stores/TagOrderStore.js

@@ -94,7 +94,7 @@ class TagOrderStore extends Store {
     _updateOrderedTags() {
         this._setState({
             orderedTags: this._state.hasSynced && this._state.hasFetchedJoinedGroups ?
-                this._state.orderedTagsAccountData || this._state.joinedGroupIds : [],
+                this._state.orderedTagsAccountData || this._state.joinedGroupIds : null,
         });
     }