If you reside in another EU Member State, you have registered as an unemployed person in Poland and you receive unemployment benefit from the Polish labour office, then you declare your revenues for tax purposes only in the country where you reside.
The Polish labour office will not withhold income tax and will not send you any information on the amounts withheld as well.
If the unemployment benefit is the only revenue received in Poland, you do not have to submit a tax return in Poland.