Fixes some antag datum related issues (#17351)

code/datums/mind.dm

@@ -1515,8 +1515,7 @@
 
 /datum/mind/proc/has_antag_datum(datum_type, check_subtypes = TRUE)
 	if(!datum_type)
-		return FALSE
-	. = FALSE
+		return
 	for(var/a in antag_datums)
 		var/datum/antagonist/A = a
 		if(check_subtypes && istype(A, datum_type))

code/modules/admin/admin.dm

@@ -661,7 +661,7 @@ GLOBAL_VAR_INIT(nologevent, 0)
 		antag_list += "Shadowling Thrall"
 	if(M.mind.has_antag_datum(/datum/antagonist/traitor))
 		antag_list += "Traitor"
-	if(M.mind.has_antag_datum(/datum/antagonist/mindslave))
+	if(M.mind.has_antag_datum(/datum/antagonist/mindslave, FALSE))
 		antag_list += "Mindslave"
 	if(isrobot(M))
 		var/mob/living/silicon/robot/R = M

code/modules/mob/living/carbon/human/life.dm

@@ -365,7 +365,7 @@
 	else
 		bodytemperature += (BODYTEMP_HEATING_MAX + (fire_stacks * 12))
 		var/datum/antagonist/vampire/V = mind?.has_antag_datum(/datum/antagonist/vampire)
-		if(V && !V.get_ability(/datum/vampire_passive/full) && stat != DEAD) // V?. doesn't work here because `has_antag_datum` return FALSE if there is no datum and ?. doesn't like that
+		if(!V?.get_ability(/datum/vampire_passive/full) && stat != DEAD)
 			V.bloodusable = max(V.bloodusable - 5, 0)
 
 /mob/living/carbon/human/proc/get_thermal_protection()