Don't allow dragging .custom-control elements on folders list

program/js/app.js

@@ -7303,7 +7303,7 @@ function rcube_webmail()
       .addEventListener('collapse', function(node) { ref.folder_collapsed(node) })
       .addEventListener('expand', function(node) { ref.folder_collapsed(node) })
       .addEventListener('search', function(p) { if (p.query) ref.subscription_select(); })
-      .draggable({cancel: 'li.mailbox.root,input,div.treetoggle'})
+      .draggable({cancel: 'li.mailbox.root,input,div.treetoggle,.custom-control'})
       .droppable({
         // @todo: find better way, accept callback is executed for every folder
         // on the list when dragging starts (and stops), this is slow, but