Fix missing stderr when the progress parameter of _clone is None

[liangjingyang]

Try to fix #1221

The to_progress_instance function will convert None to RemoteProgress instance, so the line if progress_checked is True if progress parameter is None.

[muggenhor]

Thanks for finding this! I've created a unit test that fails without and succeeds with this change (also with only the the condition change as I suggested).

[Byron]

Thanks for finding this! I've created a unit test that fails without and succeeds with this change (also with only the the condition change as I suggested).

Are you able to push it into this PR? If not I would be happy to do that for you if you post it here.

[Byron]

Once approved by @muggenhor this one should be ready to merge. Looks good to me (as the tests are green :) even though without the fix they are not).