AMI filtering shouldn't expect a LaunchTemplate version

[Sutto]

We've seen data where the LaunchTemplate (on the ASG directly)
has no version attribute at all - so we should use .get with a default
of None instead, to avoid raising an exception.

[kapilt]

thanks for the pr, I assume no version specified implies latest template version for the asg, but then using a none key here afaics will result in not finding the associated template for the asg. we'll need some additional logic to enable an asg <-> latest template version match.

[kapilt]

afaics we can just above when building up a list of template versions, we can also inject the template version None for the latest version to enable a match.

[Sutto]

Yeh, I'm trying to track down the specific cause of a None template version, but I'm guessing it
's latest (the docs specifically call out a special value, but it's a different one). I'm gonna try and track it down a bit more and update, as well as adding some tests here.