Check formname in on_receive_fields

bags.lua

@@ -48,6 +48,9 @@ for i = 1, 4 do
 end
 
 minetest.register_on_player_receive_fields(function(player, formname, fields)
+	if formname ~= "" then
+		return
+	end
 	for i = 1, 4 do
 		if fields["bag"..i] then
 			local stack = player:get_inventory():get_stack("bag"..i, 1)

callbacks.lua

@@ -49,6 +49,9 @@ minetest.register_on_joinplayer(function(player)
 end)
 
 minetest.register_on_player_receive_fields(function(player, formname, fields)
+	if formname ~= "" then
+		return
+	end
 	local player_name = player:get_player_name()
 
 	for i, def in pairs(unified_inventory.buttons) do