Yes def would not use it if the crack is just that one a new handle should fix it.
Interesting my mate and I went down to warsop to get a custom made in 2015, after a couple of games we had the same cracks as in this photo, but also shoulder cracks and other stress cracks on the side of the handle, and tiny hairlines down the back of the bat. They replaced the bat or the handle(can't remember which) and the replacement bat has exactly the same cracks as the first one and it's barely been used.
He still uses it, we didn't take it back again, and it goes fine. He couldn't be bothered to return it again.
But wouldn't recommend using it at all until it is fixed. Warsop were good they do sort out any issues
I did put me off buying any more thou, I hadn't seen this very often and I've had a few bats over the years.