How an intraday trade is treated if there are no buyers or sellers at the time of squre off?
There will be no buyers in the case of a lower circuit in the stock and if you have bought the stock, then you will have to take delivery of the stock and you can sell it the next trading day if there are buyers.
There will be no sellers if a stock hits upper circuit. In this case, if you have short-sold the stock for intraday, then this trade will go to the auction market and it will be bought there.
You can read about the consequences of short delivery here.