added defautl value to app icon for Folder.jsx

src/component/Sidebar/WorkspaceListItem.jsx

@@ -9,8 +9,6 @@ const pad = number => {
   return number.length < 2 ? pad('0' + number, 2) : number
 }
 
-
-
 const WorkspaceListItem = props => {
   return (
     <li className='sidebar__navigation__workspace__item'>

src/component/Workspace/Folder.jsx

@@ -57,7 +57,7 @@ class Folder extends React.Component {
                 {t('Folder.content_type')} :
               </div>
               <div className='folder__header__contenttype__icon'>
-                { folderData.allowed_app.map(a => <i className={app[a].icon} key={`${folderData.id}_${a}`} />)}
+                { folderData.allowed_app.map(a => <i className={(app[a] || {icon: ''}).icon} key={`${folderData.id}_${a}`} />)}
               </div>
             </div>
           </div>