Add back line removed during conflicts

Author: wilsonge

build/media_source/system/js/fields/joomla-field-subform.w-c.es6.js

@@ -288,6 +288,7 @@
       const countnew = Math.max(this.lastRowIndex, count);
       const groupnew = basename + countnew; // new group name
 
+      this.lastRowIndex = countnew + 1;
       row.setAttribute('data-group', groupnew);
 
       // Fix inputs that have a "name" attribute