Update FormItem.php

修复php8下严格模式报错问题

src/Form/FormItem.php

@@ -443,7 +443,7 @@ public function getServeRole()
         if (is_array($rules)) {
             foreach ($rules as &$rule) {
                 if (is_string($rule)) {
-                    $rule = str_replace('{{id}}', $id, $rule);
+                   $rule = str_replace('{{id}}',(string)$id, $rule);
                 }
             }
         }