Add a savefile migration to remove the device from nif paths

code/modules/client/preferences/migrations/15_nif_path.dm

@@ -0,0 +1,12 @@
+/// Moves nif stuff to it's own file
+/datum/preferences/proc/migration_15_nif_path(datum/json_savefile/S)
+	var/datum/json_savefile/new_savefile = new /datum/json_savefile(nif_savefile_path(client_ckey))
+
+	for(var/slot in 1 to config.character_slots)
+		var/list/prefs = new_savefile.get_entry("character[slot]", null)
+		if(!islist(prefs))
+			continue
+		prefs["nif_path"] = replacetext(prefs["nif_path"], "/device", "")
+		new_savefile.set_entry("character[slot]", prefs)
+
+	new_savefile.save()