Nope nope nope.
The good news is that crack isn't growing, it ends at two edges and it's behind the overflow so the entire tank isn't going to end up on the floor, but it could well end up with the contents of the sump and overflow on the floor. You could try and patch it from the inside, block the overflow weir and leave the overflow dry and drill it for an external overflow box. The risk isn't something I'd take in my home.
Either it was cracked for a while and the seller didn't know, or it was moved with the bulkheads still in the bottom and was broken along the way. You might be able to tell if you look at the crack, there's bound to be some algae and crud in the crack if it's been there a while.