improve subfield handling

Author: pxpm

src/app/Library/CrudPanel/Traits/FieldsProtectedMethods.php

@@ -254,10 +254,14 @@ protected function inferFieldTypeFromRelationType($relationType)
      */
     protected function makeSureSubfieldsHaveNecessaryAttributes($field)
     {
-        if (! isset($field['subfields'])) {
+        if (! isset($field['subfields']) || ! is_array($field['subfields'])) {
             return $field;
         }
 
+        if(! is_multidimensional_array($field['subfields'])) {
+            $field['subfields'] = [$field['subfields']];
+        }
+
         foreach ($field['subfields'] as $key => $subfield) {
             if (empty($subfield) || ! isset($subfield['name'])) {
                 abort(500, 'Subfield name can\'t be empty');