[SOLVED] leave period & strange message in coherence control

Hello,

As you will see in word next to this post, we have since version 11.1.XX an error in addition of our long time error on wbs on leave project ( in our case projet 115 leave period is wbs 00001 as our main project ... 00001 and moving them in portfolio doesn't change anything ) when tring to make coherence control

ERROR : explode(): Passing null to parameter #2 ($string) of type string is deprecated
   in projeqtor.php
   at line 4219

log :2024-01-16 10:39:42.674 ***** ERROR ***** [V11.1.2] ERROR *****
2024-01-16 10:39:42.674 ***** ERROR ***** [V11.1.2] on file '/var/www/projeqtor/tool/projeqtor.php' at line (4219)
2024-01-16 10:39:42.674 ***** ERROR ***** [V11.1.2] cause = explode(): Passing null to parameter #2 ($string) of type string is deprecated

Additionaly we also have task from leave period moving in imputation in other project ... really strange cause these tasks are linked to project 115 (leave period ).

Thanks for your advise.
LR
ubuntu 22.04 / apache / php8.1.2 / mysql 8.0.35

Thanks effectively, wbs in planning element was null !
i put values ... new troubles arrives but everything seems to go better after "coherence control & correction"
Thanks
LR