Describe the bug, provide any errors
Setup: 1.14.4 Fabric with ViaFabric installed.
If you summon a wither the bossbar will not appear on the ViaFabric client.

How can we reproduce it?
Steps to reproduce the behavior:

1. Select version 1.8 in ViaFabric and join a spigot 1.8.8 server
2. Summon a wither
3. No BossBar will appear

Expected behaviour
A BossBar showing the health of the wither

Screenshots
http://prntscr.com/t6pryu

ViaVersion Dump:

• Can't do that in ViaFabric.
  I use the latest ViaVersion and ViaFabric version (downloaded 26.06.2020)

Additional server info
No plugins were present on the test-server.

I created a new issue because the old one got closed and the bug remained

Yes (the latest one)