Added back subfieldHolder to avoid BC

Author: promatik

src/resources/views/crud/inc/form_fields_script.blade.php

@@ -151,6 +151,7 @@ class CrudField {
 
             if(!rowNumber) {
                 subfield.isSubfield = true;
+                subfield.subfieldHolder = this.name; // deprecated
                 subfield.parent = this;
             } else {
                 subfield.rowNumber = rowNumber;