Steps to reproduce:

1. Use slow web server / slow internet connection.
2. Observe network activity in Dev tools of the browser.
3. Edit a Graph widget.
4. Modify "data set label" field.
5. Wait 0.5 sec unless the configuration is sent to the server for validation.
6. Apply the configuration at this exact moment.

Result:

Form closed, modified configuration is NOT applied.

Expected:

Loader displayed until validation result received from the server.

Validation result processed as expected (either form is closed or error displayed).