Add null checks to client prefs checks

client.prefs. -> client?.prefs?.

code/modules/antagonists/_common/antag_datum.dm

@@ -181,7 +181,7 @@ GLOBAL_LIST_EMPTY(antagonists)
 
 /datum/antagonist/proc/enabled_in_preferences(datum/mind/M)
 	if(job_rank)
-		if(M.current && M.current.client && (job_rank in M.current.client.prefs.be_special))
+		if(M.current && M.current.client && (job_rank in M.current.client?.prefs?.be_special))
 			return TRUE
 		else
 			return FALSE

code/modules/antagonists/blob/blob/overmind.dm

@@ -192,7 +192,7 @@ GLOBAL_LIST_EMPTY(blob_nodes)
 		return
 
 	if (src.client)
-		if(client.prefs.muted & MUTE_IC)
+		if(client?.prefs?.muted & MUTE_IC)
 			to_chat(src, "You cannot send IC messages (muted).")
 			return
 		if (src.client.handle_spam_prevention(message,MUTE_IC))

code/modules/antagonists/clockcult/clock_mobs/_eminence.dm

@@ -80,7 +80,7 @@
 
 /mob/camera/eminence/say(message, bubble_type, var/list/spans = list(), sanitize = TRUE, datum/language/language = null, ignore_spam = FALSE, forced = null)
 	if(client)
-		if(client.prefs.muted & MUTE_IC)
+		if(client?.prefs?.muted & MUTE_IC)
 			to_chat(src, "You cannot send IC messages (muted).")
 			return
 		if(client.handle_spam_prevention(message,MUTE_IC))

code/modules/antagonists/revolution/revolution.dm

@@ -286,7 +286,7 @@
 			var/list/datum/mind/promotable = list()
 			for(var/datum/mind/khrushchev in non_heads)
 				if(khrushchev.current && !khrushchev.current.incapacitated() && !khrushchev.current.restrained() && khrushchev.current.client && khrushchev.current.stat != DEAD)
-					if(ROLE_REV in khrushchev.current.client.prefs.be_special)
+					if(ROLE_REV in khrushchev.current.client?.prefs?.be_special)
 						promotable += khrushchev
 			if(promotable.len)
 				var/datum/mind/new_leader = pick(promotable)