NullPointer 1.8 server with 1.17 protocollib

Describe the bug 1
Since I switched from build #521 to build #523 this error appears, whats wrong, or isnt there backwards compatible?
Error: https://paste.gg/p/anonymous/164d61eb3e014a67aa5e108ccd8100b0
Code: https://paste.gg/p/anonymous/da1f3c94074f4ec48b49c80faaf4b5e9
Server: 1.8.8 Paper Fork

Describe the bug 2
Since protocollib 1.17 the FLYING field isnt working.
Error: https://pastebin.com/fbQdMaxL
Server: 1.16.5 Paper

[derklaro]

Duplicate of #1274

these three minutes he was faster... what a coincidence. But the second bug he dont have :P