To reproduce:
1. Open the "TestScene" in the user-provided project
2. Select the "PlaneAnimation&Cloth" Game Object from the Hierarchy and enable it
3. Enter the play mode

Desired outcome: The editor does not crash.
Actual result: The editor crashes.

Stack trace:
(Unity) SkinnedMeshRenderer::PrepareSkinCommon
(Unity) SkinnedMeshRenderer::PrepareSkinGPU
(Unity) SkinnedMeshRenderer::UpdateSkinnedMeshes
(Unity) SkinnedMeshRendererManager::UpdateAllSkinnedMeshes
(Unity) SkinnedMeshRenderer::UpdateAllSkinnedMeshes
(Unity) UpdateClothsJob
(Unity) JobQueue::Exec
(Unity) JobQueue::ExecuteJobFromHighPriorityStack
(Unity) JobQueue::ProcessJobs
(Unity) JobQueue::WorkLoop
(Unity) Thread::RunThreadWrapper
(KERNEL32) BaseThreadInitThunk
(ntdll) RtlUserThreadStart

Reproduced with 5.6.0a1, 5.6.3f1, 2017.1.0a1, 2017.1.0f3, 2017.1.0p3, 2017.2.0b7, 2017.3.0a4
Not reproduced with 5.5.1f1, 5.5.4p3
Regression introduced in 5.6