[combat] Add safety checks to status effect data fetching logic

[Xaver-DaRed]

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• [x] I understand I should leave resolving conversations to the LandSandBoat team so that reviewers won't miss what was said.
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• [x] I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

Ensure a table entry for an status effect exists before attempting to fetch it. It seems an or 0 just doesnt cut it

Steps to test these changes

Have mobs use status effect mobskills and not see errors in log.