Handle NoneType self.mons from a pickle

[jeanconn]

Description

Handle NoneType self.mons from an old proseco pickle

Testing

• Passes unit tests linux
• Functional testing - not sure if we want to add an old pickle file to the test suite. I confirmed that with this code change I did not see the error seen in len(self.mons) not compatible with catalogs from proseco < 5.0 #157 .

Fixes #157

[jeanconn]

Another option to work around this is just to pass the call_args to (new) proseco and regenerate the catalogs, but that seems not in the spirit of things.

[taldcroft]

Agreed we should add a regression test that includes a stored pickle from proseco < 5.0 in order to avoid surprises like this. So why don't you do that as part of this PR.

Decided the regression test is needed.

[jeanconn]

Do you want to make an old pickle file or just set a new baseline with a "current" proseco pickle? And then what paces do we need to put the code through for due diligence (run review, roll options?)?

[jeanconn]

OK. I went with adding a single-obsid 4.12.1 proseco pkl file and added a test that uses some work-alike code to read the pickle, run review, and check for messages.