It's possible to go to the bar without going to the restaurant. The bar is in the basement and you get to it via the big red door next to the doors leading in to the restaurant. Unsurprisingly the bar is called The Red Door.
I've been a couple of times now, including a Friday night, and it's never been packed. The nice, or otherwise dangerous, thing is that you sit at a table and wait staff serve you all night. They are highly attentive, so you find yourself never without a drink and never moving and so the hours just pass.
It's a perfect place to go if you are looking to catch up with friends and want to be some place for an easy chit chat.