Fixed errors when joining a channel that doesn't exist yet

webapp/components/popover_list_members.jsx

@@ -57,7 +57,11 @@ export default class PopoverListMembers extends React.Component {
         const members = this.props.members;
         const teamMembers = UserStore.getProfilesUsernameMap();
         const currentUserId = UserStore.getCurrentId();
-        const ch = ChannelStore.getCurrent();
+        const ch = ChannelStore.get(this.props.channelId);
+
+        if (!ch) {
+            return null;
+        }
 
         if (members && teamMembers) {
             members.sort((a, b) => {

webapp/stores/post_store.jsx

@@ -531,8 +531,8 @@ PostStore.dispatchToken = AppDispatcher.register((payload) => {
     switch (action.type) {
     case ActionTypes.RECEIVED_POSTS: {
         const id = PostStore.currentFocusedPostId == null ? action.id : PostStore.currentFocusedPostId;
-        PostStore.checkBounds(id, action.numRequested, makePostListNonNull(action.post_list), action.before);
         PostStore.storePosts(id, makePostListNonNull(action.post_list));
+        PostStore.checkBounds(id, action.numRequested, makePostListNonNull(action.post_list), action.before);
         PostStore.emitChange();
         break;
     }