refactor: add |null in docblock (#57253)

* refactor: add |null in docblock

* Update ValidatesAttributes.php

---------

Co-authored-by: Taylor Otwell <[email protected]>

Author: alipowerful7

src/Illuminate/Validation/Concerns/ValidatesAttributes.php

@@ -277,13 +277,13 @@ protected function getDateFormat($attribute)
      * Get the date timestamp.
      *
      * @param  mixed  $value
-     * @return int
+     * @return int|null
      */
     protected function getDateTimestamp($value)
     {
         $date = is_null($value) ? null : $this->getDateTime($value);
 
-        return $date ? $date->getTimestamp() : null;
+        return $date?->getTimestamp();
     }
 
     /**