Given new state is NULL, couldn't post update

Hello dear friends. I am doing some connections with openhab, mqtt and arduino uno and I was just wondering, why i get “given new state is NULL, couldn’t post update for lamp”.
Everything is working fine, just Openhab tells me that something is wrong. The trick is that I have switch command for my lamp, so my lamp in that case received command 1 and turn light on arduino over mqtt protocol. The same thing goes when I send command OFF. It’s not such a problem, because everything is working, but I just wanna know why I get this error and make it perfect.


Switch lamp1 "Luc dnevna soba" (all) {mqtt=">[broker:home/luc:command:ON:1],>[broker:home/luc:command:OFF:0],<[broker:home/luc/state:state:default"} 


sitemap default label="Main Menu"
			Switch item=lamp1 label="Luc dnevna soba"

tnx for help

Remove the last part of your item configuration where you want to receive from your broker, make sure you have no errors.
Use any MQTT tool to check what is really coming on home/luc/# topic, then adjust you configuration accordingly.

I get back 1 or 0 on state if I understand correctly. Is code no good?