I would really like to go to bed, but the slow cooker isn't done
Warm isn't guaranteed to be safe. On some cookers it might be, but unless you've checked yours already, you can't say for sure. I suppose you could try it and check the temperature in the morning, and if it's above 140F everywhere, it's okay, but I'm not sure you want to risk that.

So I think you're stuck either cooking it overnight (on low, not warm) or moving it to the fridge and cooking more tomorrow.