Yes, it’s perfectly safe.
Your ABS system actually operates by interfering with the hydraulics in your braking system on the wheel that it detects is spinning. Having the ABS deactivated only means that your braking system is operating without interferemce, as if you never had ABS at all. Hydrauilcally it’s exactly the same as a conventional braking system without ABS.
Many of us, myself included, have had less than stellar experiences with ABS on icy surfaces. Personally, I think you’re better off without it.