PHP notices/deprecation... prevents XB to load

Marking this as related to 📌 Improve server-side error handling Active since they both have to do with error handling.

#2++

Only after that is fixed, should we tackle this one with an explicit tests. That other issue should fix this too :)

Thanks, @heyyo & @lauriii! 👍

📌 Improve server-side error handling Active has landed

If I was right in #3, then #3485878 should've fixed this too 😇