symfony/symfony-docs — pull request #4204 by xabbuh (2014-09-05 10:34:00+00:00)
Title: [Reference][Constraints] validate `null` (Expression constraint in 2.6)

| Q | A
| ------------- | ---
| Doc fix? | no
| New docs? | yes (symfony/symfony#11709)
| Applies to | 2.6
| Fixed tickets | master part of #4191

Since Symfony 2.6, the Expression constraint doesn't skip validating `null` values.

Probably, it's a good idea to merge #4202 first and rebase this then to avoid merge conflicts.