add nametag check when renaming

api.lua

@@ -3,7 +3,7 @@
 
 mobs = {}
 mobs.mod = "redo"
-mobs.version = "20180324"
+mobs.version = "20180328"
 
 
 -- Intllib
@@ -3731,6 +3731,13 @@ minetest.register_on_player_receive_fields(function(player, formname, fields)
 			return
 		end
 
+		-- make sure nametag is being used to name mob
+		local item = player:get_wielded_item()
+
+		if item:get_name() ~= "mobs:nametag" then
+			return
+		end
+
 		-- limit name entered to 64 characters long
 		if string.len(fields.name) > 64 then
 			fields.name = string.sub(fields.name, 1, 64)