Fix scrolling issue in pad when the userlist or the messenger was too big

www/pad/app-pad.less

@@ -27,6 +27,7 @@ body.cp-app-pad {
         height: 100%;
         border: 0;
         > .cke_inner {
+            overflow: hidden;
             flex: 1;
             position: unset;
             display: flex;