I believe a translation with 'him' should be accepted too. Although the pronoun is not used, the 3rd-person form of the verb is used, so we can understand it's either 'она', or 'он' (or 'оно', but things in neuter gender usually can't 'come').
Actually, this is a possible translation of the Russian sentence. I think it should be accepted. Consider using the Report button next time you get this sentence.
Given the absence of a pronoun the more natural English translation becomes "leave it until tomorrow , we're tired"