App crashes when clicking during folder scan

Hey,

As a long-time user of WinSCP, I wanted to report a persistent bug that leads to a fatal crash.
If you perform an action (like clicking another folder) while the application is busy loading a large directory in the background, it triggers a fatal error.

Steps to Reproduce:

1. Open a very large folder (containing 10k, 50k, or 100k+ files).
   
2. Navigate to a different, smaller folder and create a temporary test file.
   
3. Move this test file into the large folder.
   
4. While the cursor shows the waiting symbol (indicating the app is reloading the large directory after the file transfer), click on any other folder.
   
5. The app is waiting for a response. After about 3 minutes of unresponsiveness, the program times out, reconnecting and crashes with the following error
   
6. The app can no longer be used reliably after that and may crash at any time.
   

The same bug might exist in other parts of the app under similar conditions with large folders.

Thanks for your report. I wasn't able to reproduce the problem. Could you please record a screencast showing what exactly you are doing? Thanks.