System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX 970/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 388.13

Blender Version
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-07-16 23:38, hash: rB4a5e046c923f
Worked: (optional)

Short description of error
Blender Crashes in Movie Clip editor when in Mask mode and you click on the picture (not even drawing the mask)

Exact steps for others to reproduce the error

1. New Blender Scene
2. Open Video Clip editor
3. Load Picture ( I got same crash for PNG and EXR)
4. Change to mask mode
5. Add new mask
6. Add a new Mask layer
7. left click on the picture (no controll key or other needed)

--> quick close Option = Crash !!!!!

I hope that gives you a hint where to finde the problem. Thumbs up and regards.
Björn