Steps to reproduce:
1. Download and open attached project "Cuttingmeshes.zip"
2. Open scene "scenes/main"
3. Make sure GPU Skinning option is on in Player Settings
4. Play scene
5. In hierarchy take sword and move it to the soldier

Actual result: Upon cutting, Unity crahes
Expected: Not to crash

Tested and reproduced on:
Windows 10
Unity 5.4.0b25

Could not test in 5.3 or older due to old API.
(Neither on 5.5? Weird)