Fix DMs showing players that have cryoed (#10437)

code/modules/modular_computers/file_system/programs/generic/ntnrc_client.dm

@@ -29,6 +29,10 @@
 	if(!comp)
 		return
 
+/datum/computer_file/program/chatclient/Destroy()
+	ntnet_global.chat_clients -= src
+	return ..()
+
 /datum/computer_file/program/chatclient/Topic(href, href_list)
 	if(..())
 		return TRUE
@@ -265,6 +269,8 @@
 		if((confirm != "Yes") || (CanUseTopic(usr) != STATUS_INTERACTIVE))
 			return FALSE
 
+	ntnet_global.chat_clients -= src
+
 	channel = null
 	..(forced)
 	return TRUE