Pyxel crashes when closing
**Describe the bug**
The app crashes when clicking on the close button or pressing a specified key to close (via pyxel.quit()). The window remanins open and you have to close it from the task manager. Note: the Python Shell does restart despite this issue.
I have experienced this issue in a MSI modern and a HP laptop both bought this year and with similar characteristics.

**To Reproduce**
It happens when you close the app while it is running. 

**Desktop:**
 - OS: Windows Home 10 64-bit
 - Python 3.7
 - Pyxel 1.4.1

I hope you can help me :)
