Fix not disappearing holograms

[EpicPlayerA10]

Description

Fixes not disappearing holograms caused by delayed hologram placement when called from async ( #3176 (comment) )

Proposed changes

• Makes HologramsService#updateHologram to allows calls only from sync code. Calls from async code should not be allowed as this on its own causes undefined behaviour. For example the HologramsService#removeHologram function already does not allow async.
• Make some changes in HologramOwner#updateHologram to allow calls from async code. Checks isDeletedSoon to be sure that the hologram owner still exists.

Related Issues (if applicable)

• Holograms not disappearing again #3176

Checklist

• I have fully tested the proposed changes and promise that they will not break everything into chaos.
• I have also tested the proposed changes in combination with various popular addons and can confirm my changes do not break them.
• I have made sure that the proposed changes do not break compatibility across the supported Minecraft versions (1.16.* - 1.20.*).
• I followed the existing code standards and didn't mess up the formatting.
• I did my best to add documentation to any public classes or methods I added.
• I have added Nonnull and Nullable annotations to my methods to indicate their behaviour for null values
• I added sufficient Unit Tests to cover my code.

[github-actions]

Your Pull Request was automatically labelled as: "✨ Fix"
Thank you for contributing to this project! ❤️

[JustAHuman-xD]

I’ll try and test and review this today, long standing bug but if it’s being called async that would make sense as to why it does that weird behavior, thanks for the PR!

[github-actions]

Slimefun preview build

A Slimefun preview build is available for testing!
Commit: dd164ef3

https://preview-builds.walshy.dev/download/Slimefun/4197/dd164ef3

Note: This is not a supported build and is only here for the purposes of testing.
Do not run this on a live server and do not report bugs anywhere but this PR!

[JustAHuman-xD]

Only other thing that may or may not be a problem is the removal of the exception catching and therein logging

[EpicPlayerA10]

Only other thing that may or may not be a problem is the removal of the exception catching and therein logging

The error will be logged by java anyway because the thrown exception from getHologram will be propagated to the stacktrace. I think it is better to throw exception and stop execution of further code where getHologram was called, than only printing error in the console and allowing further code execution while creating undefined behaviour.