Fixes modal example code

Author: jlukic

server/documents/modules/modal.html.eco

@@ -246,7 +246,7 @@ themes      : ['Default', 'Material']
           <div class="header">
             Profile Picture
           </div>
-          <div class="content">
+          <div class="image content">
             <div class="ui medium image">
               <img src="/images/avatar/large/chris.jpg">
             </div>