Ruling bisharp

[lpdmaster01]

http://pokebeach.com/scans/noble-victories/76-bisharp.jpg

this bisharps night slash says swich this pokemon
if you dont have a have a pokemon on the bench can you still use the attack

 

[Sleeping Snorlax]

Yes you may still use the attack even if you have no bench. Now, if the attack said it will fail if you can't switch then it wouldn't work.