LibVLC login dialog callback different behaviour Linux vs Windows

Using LibVLC 4.x and libvlc_dialog_set_callbacks, I add handlers for the error and login dialogs.

I trigger a login dialog by attempting to play a protected HTTP stream.

In the login handler, rather than posting a valid login, I simply call libvlc_dialog_dismiss to cancel the dialog.

On Linux (tested at commit 37cab63f), this results in a subsequent invocation of the error callback with error text "VLC is unable to open the MRL".

On Windows (tested with nightly build Win64 20220506-0423), there is no error callback invoked.

(Note that it in fact invokes the login callback a second time, but that is probably unrelated, see #26861)

The same difference in behaviour is apparent if triggering a question dialog callback rather than login.

For example, I have a test that provokes an invalid certificate question. Cancelling that dialog on Linux results in an error dialog callback, but not on Windows.