Fix: show right pane in mockup

mockup/controlbox.html

@@ -244,7 +244,7 @@
                 </div>
               </div>
 
-                <div id="chatrooms" class="controlbox-pane" style="">
+                <div id="chatrooms" class="controlbox-pane" style="display: none">
                     <form class="pure-form pure-form-stacked converse-form add-chatroom" action="" method="post">
                         <fieldset>
                             <legend>Join an existing room or create a new one</legend>