Fixes sentry targeting xenos inside of vents (#6223)

# About the pull request

Closes #6110, #5556. Honestly I was unable to reproduce the issue, but
this seems like it should work regardless of the original problem.


# Changelog
:cl:
fix: Fixes sentries firing at xenos while vent crawling.
/:cl:

---------

Co-authored-by: DOOM <N/A>

code/modules/defenses/sentry.dm

@@ -365,7 +365,7 @@
 				targets.Remove(A)
 				continue
 
-			if(M.get_target_lock(faction_group) || M.invisibility || HAS_TRAIT(M, TRAIT_ABILITY_BURROWED))
+			if(M.get_target_lock(faction_group) || M.invisibility || HAS_TRAIT(M, TRAIT_ABILITY_BURROWED) || M.is_ventcrawling)
 				if(M == target)
 					target = null
 				targets.Remove(M)