UE5.4 project crash

Hey, just wondering if anyone can help with this?

I upgraded my project to 5.4 and every time I compile my player BP it crashes with this error…

Assertion failed: InBoneContainer && InBoneContainer->IsValid() [File:D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Public\BonePose.h] [Line: 151]