System Information
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 950M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 431.60

Blender Version
Broken: version: 2.81 (sub 4), branch: master, commit date: 2019-08-31 11:22, hash: rB82ef1edce4a2

Short description of error
Adding modifiers on grease pencil causes crash.

Exact steps for others to reproduce the error
1: Add a "Blank" grease pencil
2: Switch to draw mode
3: Draw a single stroke
4: Go back to object mode
5: Add array modifier(or any modifier for that matter)
6: Crash

With .blend provided just add a array modifier.