[MIRROR] Fixes some runtimes in pathfinding (and bonus) [MDB IGNORE] (#25969)

* Fixes some runtimes in pathfinding (and bonus) (#80735)

## About The Pull Request

Found these while running a test server all night. I am not sure if the
second one really causes issues because `.` is being set to something
but it is is certainly polluting the runtime logs.

Also fixes an unrelated runtime with one of the admin verbs, where it
would runtime if you canceled out of the input prompt.

## Why It's Good For The Game

Less runtime spam.

![IklvTShHJB](https://github.com/tgstation/tgstation/assets/13398309/2441ad6b-67b7-4d65-83a3-eabba4516fe9)

![veGkt0Eyul](https://github.com/tgstation/tgstation/assets/13398309/e99eced9-89e6-4065-93d9-578795ddbd8d)

## Changelog

🆑
fix: fixes some runtimes in pathfinding code, as well as one in the give
direct control admin verb
/🆑

* Fixes some runtimes in pathfinding (and bonus)

---------

Co-authored-by: Bloop <13398309+vinylspiders@users.noreply.github.com>

code/modules/admin/verbs/debug.dm

@@ -217,6 +217,8 @@
 		if(tgui_alert(usr,"This mob is being controlled by [M.key]. Are you sure you wish to give someone else control of it? [M.key] will be made a ghost.",,list("Yes","No")) != "Yes")
 			return
 	var/client/newkey = input(src, "Pick the player to put in control.", "New player") as null|anything in sort_list(GLOB.clients)
+	if(isnull(newkey))
+		return
 	var/mob/oldmob = newkey.mob
 	var/delmob = FALSE
 	if((isobserver(oldmob) || tgui_alert(usr,"Do you want to delete [newkey]'s old mob?","Delete?",list("Yes","No")) != "No"))