Describe the bug
Crash when clicked there is only one advancement in one category. I guess.

To Reproduce
Watch the screenshot.

Expected behavior
No crash.

Screenshots

Debugging
crash-2022-07-04_11.13.24-client.txt

Additional context

Thanks for the report. I will prepare a fix for this.
The problem is that after opening the normal or a modded advancement screen, I need to reload all advancements events and data.
I reload the advancements lazy to make sure it's not blocking the user or the client.

But it could happen that because of this some advancements are not loaded which leads to the issue.
The fix will avoid the crash for this kind of issues.