Ensures popping lgpo.secedit_data does not throw KeyError

[lorengordon]

What does this PR do?

Ensures popping lgpo.secedit_data does not throw KeyError

What issues does this PR fix or reference?

Fixes #56288

Previous Behavior

See linked issue

New Behavior

Avoids a KeyError when using lgpo.set with secedit policies

Tests written?

[NOTICE] Bug fixes or features added to Salt require tests.
Please review the test documentation for details on how to implement tests into Salt's test suite.

Yes

Commits signed with GPG?

Yes

Please review Salt's Contributing Guide for best practices.

See GitHub's page on GPG signing for more information about signing commits with GPG.

[lorengordon]

Just added a test. Turns out this wasn't caught before because the tests were only exercising the _modal_sets logic path in set_... This bug is in the _secedits logic path.

[lorengordon]

@waynew Is salt still doing bug fixes to 2018.3 and 2019.2? Would it be possible to backport this?

[waynew]

@lorengordon No - per https://github.com/saltstack/salt-enhancement-proposals/blob/master/accepted/0014-dev-overhaul.md (and https://docs.google.com/document/d/1DfOGVmsQaqr3rZrFqo-gf9wm1mYM-nwa5a1zROatCXQ/edit) old branches are supported, but they no longer receive active development.

To receive new fixes and features one will either need to upgrade, or backport changes themselves.

But to continue to receive new fixes and features, the recommended approach is to upgrade (after testing, of course).

[lorengordon]

Ok, it's just going to be a loooooong road before 3000 stable enough for us to switch. Sigh.