failed assertions and uncaught exceptions when a receiver gets disconnected

Created by: rathann

Information

• Solaar version (solaar --version and git describe --tags): 1.0.4
• Distribution: Fedora 32
• Kernel version (ex. uname -srmo): Linux 5.8.16-200.fc32.x86_64 x86_64 GNU/Linux
• Output of solaar show for the target device (if applicable): N/A

Describe the bug solaar sometimes fails with failed assertion or unhandled exception when the receiver gets disconnected in the middle of operation.

To Reproduce Steps to reproduce the behavior:

1. Disconnect the receiver or the USB hub to which it's connected (or cut power to it).
2. Solaar sometimes fails with AssertionError or NoReceiver exception.

Screenshots N/A

Additional context Downstream bug reports:

• AssertionError in tray.py:_update_menu_item
• AssertionError in window.py:_device_row
• NoReceiver exception due to invalid file descriptor (OSError) in base.py:_skip_incoming called all the way up from window.py:_device_selected

If you want, I can split these three into separate bug reports instead, but they seem to have a common theme of the receiver getting disconnected from the USB bus for one reason or another.