Explorer: click open button without selecting any item

[kangz12345]

Describe the bug

When you click the open button without selecting any item (the initial state), the program aborts. Or the reason is that the file tree is empty (when I cannot access the artiq-proxy or the file tree is actually empty), I did not check which is the reason.

Expected behavior

Open button is disabled or nothing happens even if I click the open button.

To Reproduce

Steps to reproduce the behavior:

1. I tested this in giwon2004/63/scheduler branch.
2. Run iquip by console command qiwis in the repository.
3. No access to artiq-proxy server.
4. The file tree is empty
5. Click the open button.

Expected causes and correction methods

Check if experimentFileItem is None in openExperiment(). Or do some more signal-slot stuffs to disable the open button when no file is selected.

Screenshots

[BECATRUE]

I reproduced this situation, and I think both reasons you suggested look correct😂

[kangz12345]

Thank you for the investigation! Then the first reason (not selected) is correct (because when the file tree is empty, we cannot select any item).