AbstractSSHClient login is crashing, if keep_alive_interval is not given as argument

If you call the login and no keep_alive_interval, then the keep_alive_inteval is set to None,
with this the following line will not work:

(line 203) keep_alive_interval = int(TimeEntry(keep_alive_interval).value)

Start in AbstractSSHClient.login at the reported line 203 and reproduce a login call without keep_alive_interval. Confirm the failure caused by the None value, then verify that login completes successfully when the argument is omitted.

Written by the indexing model from the issue text.