PHP Warning after installing 1.12.2

[hgpit]

Just upgraded Additional Fields plugin from 1.12.0 to 1.12.2 on GLPI v9.5.2, and now we get this following PHP warning:

Any tips to fix?

[hgpit]

Tried logging out and back in, but issue persists.

[eduardomozart]

I'm also receiving this issue into GLPI 9.5.4 and PHP 7.3.

[hgpit]

Thanks for fixing :)