minor #19331 [Form][#16809] add missing pad property (xabbuh)

This PR was merged into the 3.2-dev branch.

Discussion
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[Form][#16809] add missing pad property

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #16809 (comment)
| License       | MIT
| Doc PR        |

Commits
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647e6ba [#16809] add missing pad property

src/Symfony/Component/Form/Extension/Core/DataTransformer/DateIntervalToArrayTransformer.php

@@ -40,6 +40,7 @@ class DateIntervalToArrayTransformer implements DataTransformerInterface
         self::INVERT => 'r',
     );
     private $fields;
+    private $pad;
 
     /**
      * @param string[] $fields The date fields