fix burrowed burrower should not be hit by gau

[cuberound]

About the pull request

adds check for being burrowed to direct GAU damage

Explain why it's good for the game

burrowed burrower should not be hit by any effect, bugfix (untested, not good at testing stuff that reqires checking more mobs but should work"

Testing Photographs and Procedure

Screenshots & Videos

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Changelog

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fix: GAU can not hit burrowed burrower
/:cl:

[github-actions]

This PR has been inactive for long enough to be automatically marked as stale. This means it is at risk of being auto closed in ~ 7 days, please address any outstanding review items and ensure your PR is finished, if these are all true and you are auto-staled anyway, you need to actively ask maintainers if your PR will be merged. Once you have done any of the previous actions then you should request a maintainer remove the stale label on your PR, to reset the stale timer. If you feel no maintainer will respond in that time, you may wish to close this PR youself, while you seek maintainer comment, as you will then be able to reopen the PR yourself

[Drulikar]

I do not think this change necessary. Burrower can already burrow out of the way, they don't need additional help. At a bare minimum they could take reduced damage for being underground, but again I don't think they need a buff.