Avoid KeyError if cron change does not include a diff (#32513)
Avoid KeyError if cron change does not include a diff (#32513)

Prevents this exception:

    File "/tmp/saltenv/lib/python2.7/site-packages/salt/state.py", line 1703, in call
      **cdata['kwargs'])
    File "/tmp/saltenv/lib/python2.7/site-packages/salt/loader.py", line 1661, in wrapper
      return f(*args, **kwargs)
    File "/tmp/saltenv/lib/python2.7/site-packages/salt/states/cron.py", line 567, in file
      ret['changes'] = {'diff': ret['changes']['diff']}
    KeyError: 'diff'

As far as I can tell this line is a noop at best
saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt