remove a comma

client/coral-plugin-questionbox/QuestionBox.js

@@ -3,7 +3,7 @@ const packagename = 'coral-plugin-questionbox';
 
 const QuestionBox = ({enable, content}) =>
 <div
-  className={`${packagename}-info ${enable ? null : ', hidden'}` }>
+  className={`${packagename}-info ${enable ? null : 'hidden'}` }>
   {content}
 </div>;