Playing on an Enigmatica 6 server, I encountered this crash (repeated it to make sure it was possible to replicate):
crash-2021-05-30_14.44.05-client.txt
crash-2021-05-30_14.55.36-client.txt
Replication steps:

• Equip a falconry hood on a tamed falcon
• Grab the falcon using a falconry glove
• Punch the air to send the falcon out <- crash occurs at this point

It's more helpful for the devs if you paste the log into a paste site, but at least you didn't embed it into the post (:

Anyway, unless I'm reading this wrong (which is likely tbh, I don't have much/any experience in this field) this looks like a conflict between Tetra and Alex's, somehow:

java.lang.NullPointerException: Unexpected error
at se.mickelus.tetra.effect.gui.RevengeGui.update(RevengeGui.java:47) ~[?:3.10.0] {re:classloading}
at se.mickelus.tetra.effect.gui.AbilityOverlays.onRenderOverlay(AbilityOverlays.java:40) ~[?:3.10.0] {re:classloading}

It's a known issue: mickelus/tetra#422 and it's fixed in the latest Tetra. I guess someone with magic powers should mark it as Fixed in Next Release, right?