blank and filled now support stringable (#51300)

* filled and blank works with `Stringable`

* unnecessary

---------

Co-authored-by: stefan.riedel <stefan.riedel@arbeitsmedizin.de>

helpers.php

@@ -60,6 +60,10 @@ function blank($value)
             return count($value) === 0;
         }
 
+        if ($value instanceof Stringable) {
+            return $value->trim()->toString() === '';
+        }
+
         return empty($value);
     }
 }