Any entity ( except players ) getting wither effect will cause players nearby to be kicked

[thedankeststorm]

Describe the bug
Applying wither effect to any entities ( except players ) within the player's rendering range would cause that player to be kicked with the following error message:

Internal Exception: io.netty.handler.codec.EncoderException: java.lang.NullPointerException: Cannot invoke "com.github.retrooper.packetevents.protocol.world.damagetype.DamageType.getId(com.github.retrooper.packetevents.protocol.player.ClientVersion)" because "this.sourceType" is null

Software brand
Purpur Version: 1.21.4-2376-4bf1b98 (MC: 1.21.4)

Plugins

How To Reproduce
Steps to reproduce the behavior:

1. Apply wither effect to any entity except for players.
2. Any players near that entity or within rendering distance would be kicked.

Expected behavior
No player would be kicked.

Screenshots

Additional context
None available.

[booky10]

Do you have any datapacks installed and what's your client version?

[thedankeststorm]

Do you have any datapacks installed and what's your client version?

Client is 1.21.4