Incompatibility with Purpur (Paper fork)

Summary

Upon loading the plugin on a Purpur server, it spits an error that does not arise on Paper.

Steps to reproduce

1. Download Purpur here: https://ci.pl3x.net/job/Purpur/
2. Boot the Purpur server with MythicMobs in the plugins folder.
3. Observe the above error message.

Current behavior

Nothing bad happens after this when the server is idle, but I am concerned about the impact it may have on certain mob packs.

Intended correct behavior

I would expect there to be no compatility issue and, by extension, no error message.

Server log file

https://pastebin.com/AgJYxiLp

Debug log snippet

The bugged behaviour occurs in the above startup log from lines 731 to 746.

Proposed fixes

I asked the folks in the Purpur community about this and they helpfully directed me towards a bug (and its respective fix) that was recently found in another plugin and appears to be caused by the same type of issue: https://github.com/elBukkit/MagicPlugin/issues/816