修复工具表单使用分列布局报错问题

src/Form/Layout.php

@@ -117,6 +117,12 @@ class Layout
             $html .= $column->render();
         }
 
+        $this->form->fields()->each(function ($field) use (&$html) {
+            if ($field instanceof Form\Field\Hidden) {
+                $html .= $field->render();
+            }
+        });
+
         return $html.'</div>';
     }
 }