Fixes Posibrains/MMI pilots being permaslept on mech destruction (#3101)

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## About The Pull Request

Fixes #2658

Mech destruction applied sleep on the occupant no matter what, even if
it couldn't naturally wake up from sleep. It checks for human mobs now
so we shouldnt get edge cases like this.

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## Why It's Good For The Game

Bug fix

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## Changelog

:cl:
fix: Posibrains/MMI pilots being permaslept on mech destruction
/:cl:

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---------

Signed-off-by: Gristlebee <[email protected]>
Co-authored-by: Theos <[email protected]>

code/game/mecha/mecha.dm

@@ -158,7 +158,7 @@
 	return cell
 
 /obj/mecha/Destroy()
-	if(occupant)
+	if(occupant && iscarbon(occupant))
 		occupant.SetSleeping(destruction_sleep_duration)
 	go_out()
 	var/mob/living/silicon/ai/AI