Fix exception message when entering invalid characters

[ghost]

Questions	Answers
Description?	An exception is displayed when creating a list with an invalid name
Type?	bug fix
BC breaks?	no
Deprecations?	no
Fixed ticket?	Fixes 28835
How to test?	Try to enter test = test when you create a wish list
Possible impacts?
Sponsor company	@friends-of-presta

[sLorenzini]

hello @okom3pom,

Thank you for this PR.
Tested on develop, 178x & 80x versions, PHP 7.3

Error message is well displayed instead of 500 error ✅

• develop

developwishlist.mp4

• 178x

178wishlist.mp4

• 80x

80xwishlist.mp4

QA approved ✅

Thanks

[jolelievre]

Thanks @okom3pom and @sLorenzini