I'm not really the dissenting vote here.
But...
I would say - it depends...
What happened to make you lose your visor (perhaps others know the backstory that I don't)? There's not enough information here.
Did you do a face plant, in which your helmet contacted the ground and the visor popped off? Did you hit a tree or some overhang that ripped it off?
If the helmet didn't suffer a blow, and it's only the plastic decorative covering over it that is cracked because of the visor ripping off, then probably the protective shock-absorbing foam is likely not compromised and the helmet is fine....if just a little beat-up looking.
That being said.....
When it comes to the head....I would probably say...when it doubt, better to err on the side of safe, rather than sorry. Sure, the helmet is *probably* fine...but why risk it? If you are more comfortable with a new helmet....then get one.