fix for the file explorer progress bar issue (related to network disconnection)

[safisa]

What it does

Fixes:
#13216

How to test

1. set the frontendConnectionTimeout to some high value (e.g 15000ms)
2. set the reloadOnReconnect to false
3. do a network disconnection (or just a web-socket disconnection)
4. expand any folder in the file explorer
5. reconnect back
6. try to expand the folder again: the spinner and progress bar should disappear

Follow-ups

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines