Fix AttributeErrors for stop and info commands

[radomirbosak]

The AttributeError was causes by this line:

last_build = job_info.get('lastBuild', {})
...
last_build.get('something')

If the job_info var contains the lastBuild key, but it's None, the result is still None and not empty dict.

This reformulation should fix it:

last_build = job_info['lastBuild'] or {}

The empty dict gets used whenever job_info['lastBuild'] evaluates as False (None does evaluate to False)

[LD250]

Thank you for fix, @radomirbosak !