Merge pull request #7308 from Citadel-Station-13/kevinz000-patch-9

protects load_mentors from accidental wipe due to advproccall interrupting sql operations

modular_citadel/code/modules/mentor/mentor.dm

@@ -58,6 +58,7 @@ GLOBAL_PROTECT(mentor_href_token)
 	return "mentor_token=[RawMentorHrefToken(forceGlobal)]"
 
 /proc/load_mentors()
+	usr = null
 	GLOB.mentor_datums.Cut()
 	for(var/client/C in GLOB.mentors)
 		C.remove_mentor_verbs()
@@ -87,4 +88,4 @@ GLOBAL_PROTECT(mentor_href_token)
 
 // new client var: mentor_datum. Acts the same way holder does towards admin: it holds the mentor datum. if set, the guy's a mentor.
 /client
-	var/datum/mentors/mentor_datum
+	var/datum/mentors/mentor_datum