Fix missing cell borders for table with merged cells

utility.js

@@ -39,7 +39,7 @@ module.exports = {
       if (noReplaceUI) return s;
 
       s = s.split('<pre>').join('<div class="ui existing segment"><pre style="margin-top: 0; margin-bottom: 0; ">').split('</pre>').join('</pre></div>')
-           .split('<table>').join('<table class="ui celled table">')
+           .split('<table>').join('<table class="ui structured celled table">')
            .split('<blockquote>').join('<div class="ui message">').split('</blockquote>').join('</div>');
 
       let jsdom = new JSDOM(), document = jsdom.window.document;