App Labels: empty parent label for is group fie;d

smart_service/masters/doctype/app_labels/app_labels.js

@@ -22,6 +22,9 @@ frappe.ui.form.on('App Labels', {
         }
     },
     validate: function (frm) {
+        if (frm.doc.is_group) {
+            frm.doc.parent_app_labels = null
+        }
         if (frm.doc.english_label) {
             if (frm.doc.english_label.length > 100) {
                 frappe.msgprint("<b>English Label :</b> Only <b> 50 </b> characters allowed")