Fix of SymfonyForm error

[oallain]

Q	A
Branch?	1.5
Bug fix?	yes
New feature?	no
Related tickets

Fix of error :

request.CRITICAL: Uncaught PHP Exception Symfony\Component\Form\Exception\LogicException: "Cannot check if an unsubmitted form is valid. Call Form::isSubmitted() before Form::isValid()." at /home/site/vendor/symfony/form/Form.php line 765 {"exception":"[object] (Symfony\\Component\\Form\\Exception\\LogicException(code: 0): Cannot check if an unsubmitted form is valid. Call Form::isSubmitted() before Form::isValid(). at /home/site/vendor/symfony/form/Form.php:765)"} []

[GSadee]

Thank you, Olivier! 🎉