I am not sure which part of your calculations you refer to, but yes, it still seems as if you were missing a thing.
You were perfectly OK up to the "100g of ice at -24.8°C and 50 g of water at 0°C", but this is where you got confused.
Ice will be warming up and the water will freeze. You have already checked that there is not enough ice to absorb all the heat water is capable of loosing while freezing. You have already correctly calculated mass of water that will freeze.
For some reason you are still not seeing that after the freezing ends you have some water left (water at 0°C), some freshly created ice (at 0°C), and 100 g of old ice, that was heat up to 0°C. As everything now has identical temperature no further changes are possible, and the system is in the thermal equilibrium.