Sasha sometimes does this too, when she's in (our) bed for the night and we need to take her out for the "last call". We just tell her to stop, and pick her up anyway. It's a little disconcerting, but we feel we can't give in to it. Ever since we've not backed away, it occurs much less frequently.
It's really more of a grumble than a growl.... no teeth or anything!