ErrorHandler::userMessage only handled RuntimeException, but all validation
throws in ThesisCreateController and ThesisEditController use plain Exception.
This caused user-friendly messages like 'Le champ Nom/Prénom/Pseudo est requis'
to fall through to the 'Une erreur inattendue est survenue…' generic message.
Fix: add Exception check (after PDOException, since PDOException extends it)
so all validation exceptions pass their message through.
