checks: Properly handle lack of OBS version

[Penwy]

Description

This lets the analyzer properly handle the lack of an identifiable OBS version line, and report it as "Unparseable version" instead of erroring out.
This is done by propagating the None into the version parser, which will be processed as unparseable.

Motivation and Context

Analyzer errors out if no obs version line is found.

How Has This Been Tested?

Ran on a log without any version line, noticed correct print instead of error.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[RytoEX]

This is probably fine, but I'll let this sit overnight in case someone sees a reason this should not be merged.

[RytoEX]

Nit: obs -> OBS