Steps:
1. Download the project attached in comment (Legacy Simviz Test.zip (19.7 KB) )
2. Open project
3. Make sure you are using DX12 Editor (PlayerSettings>Other Settings>Graphics API list set DX12 to the top)
4. Make sure sceneview is opened and visible
5. Drag and drop the script "HandlesTest" to any GameObject on scene to add the component
6. Editor freezes and crashes

========== OUTPUTTING STACK TRACE ==================

0x00007FF6046C1F44 (Unity) GfxDeviceD3D12Base::DrawBuffersCommon
0x00007FF6046C16AE (Unity) GfxDeviceD3D12Base::DrawBuffers
0x00007FF60471793B (Unity) GfxDeviceWorker::RunCommand
0x00007FF60471B22B (Unity) GfxDeviceWorker::RunExt
0x00007FF60471B5E8 (Unity) GfxDeviceWorker::RunGfxDeviceWorker
0x00007FF60558C3A3 (Unity) Thread::RunThreadWrapper
0x00007FFD2E8D4034 (KERNEL32) BaseThreadInitThunk
0x00007FFD30E53691 (ntdll) RtlUserThreadStart

========== END OF STACKTRACE ===========

Reproducible: 2019.3.0a11, 2019.3.0a8, 2019.3.0a2, 2019.1.13f1, 2019.1.0b9
Not-reproducible: 2019.1.0a9, 2018.4.5f1, 2018.2.20f1, 2017.4.31f1
Not-reproducible on DX11