Fatal error: Can't use function return value with update V7.0.0.1 and V7.0.0.0

After update to V7.0.0.0 or V7.0.0.1 i obtain this error

Fatal error: Can't use function return value in write context in /var/www/html/projeqtor/tool/projeqtor.php on line 939
just after update

I temporary change !empty by !trim

I think this caused by error after personalized screen deletion

trace in log :
2018-03-26 11:05:42.510 ===== TRACE ===== === SCREEN CUSTOMIZATION ISSUE =====================================
2018-03-26 11:05:42.511 ===== TRACE ===== Certaines customisations d'écran ne sont pas cohérentes :
2018-03-26 11:05:42.512 ===== TRACE ===== - Livrable
2018-03-26 11:05:42.513 ===== TRACE ===== - Session de test
2018-03-26 11:05:42.514 ===== TRACE ===== Veuillez accéder à  chacun de ces écrans sur le plugin de customisation (la version 5.0 ou supérieure est requise)

I delete customized screen "livrable"
But not show something wrong in "Session de test"

Thanks for your help