Fix some odd edge-cases with head/face protection (#6523)

## About The Pull Request

This refactors `/mob/living/carbon/is_mouth_covered`,
`/mob/living/carbon/is_eyes_covered`, and
`/mob/living/carbon/is_pepper_proof` to check ALL slots for the desired
protection.

If a mask has the `HEADCOVERSMOUTH` flag, _it will still count as
covering their mouth like a helmet would_.

The first example I could think of is the damned rabbit mask - it had
`HEADCOVERSMOUTH`, and the examine would say it would protect against
facehuggers, but it does not.

## Why It's Good For The Game

bugfix

## Changelog
:cl:
fix: Fixed some weird edge cases with helmets/masks/etc that are
supposed to cover your eyes or mouth.
fix: The Damned Rabbit Mask now actually blocks facehuggers like the
examine says it should.
/:cl:

Author: Absolucy

code/modules/mob/living/carbon/alien/special/facehugger.dm

@@ -156,9 +156,10 @@
 						span_userdanger("[src] leaps at your face!"))
 
 	// probiscis-blocker handling
-	if(target.is_mouth_covered(ITEM_SLOT_HEAD))
-		target.visible_message(span_danger("[src] smashes against [target]'s [target.head]!"), \
-							span_userdanger("[src] smashes against your [target.head]!"))
+	var/obj/item/blocking_item = target.is_mouth_covered(ITEM_SLOT_HEAD)
+	if(blocking_item)
+		target.visible_message(span_danger("[src] smashes against [target]'s [blocking_item]!"), \
+							span_userdanger("[src] smashes against your [blocking_item]!"))
 		Die()
 		return FALSE
 

code/modules/mob/living/carbon/carbon_defense.dm

@@ -27,34 +27,35 @@
 	else
 		. += E.bang_protect
 
-/mob/living/carbon/is_mouth_covered(check_flags = ALL)
-	if((check_flags & ITEM_SLOT_HEAD) && head && (head.flags_cover & HEADCOVERSMOUTH))
-		return head
-	if((check_flags & ITEM_SLOT_MASK) && wear_mask && (wear_mask.flags_cover & MASKCOVERSMOUTH))
-		return wear_mask
-
+/mob/living/carbon/proc/check_equipment_cover_flags(flags = NONE)
+	for(var/obj/item/thing in get_equipped_items())
+		if(thing.flags_cover & flags)
+			return thing
 	return null
 
-/mob/living/carbon/is_eyes_covered(check_flags = ALL)
-	if((check_flags & ITEM_SLOT_HEAD) && head && (head.flags_cover & HEADCOVERSEYES))
-		return head
-	if((check_flags & ITEM_SLOT_MASK) && wear_mask && (wear_mask.flags_cover & MASKCOVERSEYES))
-		return wear_mask
-	if((check_flags & ITEM_SLOT_EYES) && glasses && (glasses.flags_cover & GLASSESCOVERSEYES))
-		return glasses
+/mob/living/carbon/is_mouth_covered(check_flags = ALL)
+	var/needed_coverage = NONE
+	if(check_flags & ITEM_SLOT_HEAD)
+		needed_coverage |= HEADCOVERSMOUTH
+	if(check_flags & ITEM_SLOT_MASK)
+		needed_coverage |= MASKCOVERSMOUTH
+	return check_equipment_cover_flags(needed_coverage)
 
-	return null
+/mob/living/carbon/is_eyes_covered(check_flags = ALL)
+	var/needed_coverage = NONE
+	if(check_flags & ITEM_SLOT_HEAD)
+		needed_coverage |= HEADCOVERSEYES
+	if(check_flags & ITEM_SLOT_MASK)
+		needed_coverage |= MASKCOVERSEYES
+	if(check_flags & ITEM_SLOT_EYES)
+		needed_coverage |= GLASSESCOVERSEYES
+	return check_equipment_cover_flags(needed_coverage)
 
 /mob/living/carbon/is_pepper_proof(check_flags = ALL)
 	var/obj/item/organ/internal/eyes/eyes = get_organ_by_type(/obj/item/organ/internal/eyes)
-	if(eyes && eyes.pepperspray_protect)
+	if(eyes?.pepperspray_protect)
 		return eyes
-	if((check_flags & ITEM_SLOT_HEAD) && head && (head.flags_cover & PEPPERPROOF))
-		return head
-	if((check_flags & ITEM_SLOT_MASK) && wear_mask && (wear_mask.flags_cover & PEPPERPROOF))
-		return wear_mask
-
-	return null
+	return check_equipment_cover_flags(PEPPERPROOF)
 
 /mob/living/carbon/check_projectile_dismemberment(obj/projectile/P, def_zone)
 	var/obj/item/bodypart/affecting = get_bodypart(def_zone)