[MIRROR] Fixes some issues with slime feeding (#708) (#1772)

* Fixes some issues with slime feeding (#81166)

## About The Pull Request

Using feed while feeding on someone will now unbuckle you rather than
prompt you to buckle to someone else like it's supposed to
The list of people to buckle to no longer includes dead people (which is
beneficial for the last fix)
If there's only one person to buckle to then it will skip the UI and eat
that person.

## Why It's Good For The Game

Fixes to slime.

## Changelog

:cl:
fix: Slimes using Feed while buckled now stops feeding.
fix: Slimes are no longer prompted to feed off of dead people.
fix: Slimes that can only feed onto one person now immediately feeds off
of them.
/:cl:

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* Fixes some issues with slime feeding

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Co-authored-by: NovaBot <[email protected]>
Co-authored-by: John Willard <[email protected]>
Co-authored-by: Ghom <[email protected]>

code/modules/mob/living/simple_animal/slime/powers.dm

@@ -30,11 +30,19 @@
 	if(stat)
 		return FALSE
 
+	if(buckled)
+		stop_feeding()
+		return TRUE
+
 	var/list/choices = list()
 	for(var/mob/living/nearby_mob in view(1,src))
-		if(nearby_mob != src && Adjacent(nearby_mob))
+		if(nearby_mob != src && Adjacent(nearby_mob) && nearby_mob.appears_alive())
 			choices += nearby_mob
 
+	if(length(choices) == 1)
+		start_feeding(choices[1])
+		return TRUE
+
 	var/choice = tgui_input_list(src, "Who do you wish to feed on?", "Slime Feed", sort_names(choices))
 	if(isnull(choice))
 		return FALSE