Template.afArrayField_bootstrap3.helpers({
  panelClass: function() {
    return this.atts.panelClass || 'panel-default';
  },
  headingClass: function() {
    return return this.atts.headingClass || '';
  }
});

@@ -160,23 +160,16 @@
  return 
-return 
 this.att

fix Unexpected token (6:11)