Open scene Tests/11_ParticleTests_LightsModule in the attached project and press Play in the Editor. It will crash after 3-5 seconds with the following stacktrace:

0x0000000140924596 (Unity) SharedLightData::Precalc
0x0000000140E20120 (Unity) LightsModule::AddCustomLights
0x0000000140E6C8A9 (Unity) ParticleSystem::AddCustomLights
0x00000001408DE2FA (Unity) Matrix3x4f::Transfer<JSONWrite>
0x00000001408DE91D (Unity) AddActiveLocalLights
0x000000014089D461 (Unity) Camera::ThreadedCleanup
0x0000000140C7C529 (Unity) JobQueue::Exec
0x0000000140C7B528 (Unity) JobQueue::Steal
0x0000000140C7B8E7 (Unity) JobQueue::ExecuteJobFromQueue
0x0000000140C7C944 (Unity) JobQueue::ProcessJobs
0x0000000140C7CA2B (Unity) JobQueue::WorkLoop
0x00000001410D635C (Unity) Thread::RunThreadWrapper
0x00007FF9F3468364 (KERNEL32) BaseThreadInitThunk
0x00007FF9F35E5E91 (ntdll) RtlUserThreadStart

The scene works fine in Unity 5.5.0p1, but is broken in 5.6, at least since alpha 4, so this is a regression