System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce GTX 1080/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 441.66

Blender Version
Broken: version: 2.91.0 Alpha, branch: Unknown, commit date: Unknown Unknown, hash: 3d78e98d52d3107aebdea119727ed909acbbc5f5
Worked: (newest version of Blender that worked as expected)

Short description of error
I'm getting an assert failure on (fcurve.c) BKE_fcurve_active_keyframe_set()

Exact steps for others to reproduce the error
Select a keyframe co then try to select the handle.