Update FileRule.php

文件验证不通过，是不是第42行少了一个"!"

src/validator/src/Rule/FileRule.php

@@ -39,7 +39,7 @@ public function validate(array $data, string $propertyName, $item, $default = nu
             $message = (empty($message)) ? sprintf('%s must exist!', $propertyName) : $message;
             throw new ValidatorException($message);
         }
-        if (isset($data[$propertyName])) {
+        if (!isset($data[$propertyName])) {
             throw new ValidatorException($message);
         }
         foreach ($filesFields as $key => $field) {