You really don't have to panic about snails starving to death from a total lack of food in your tank. They will be the last to die – about 25 years after everything else...
Actually its not at all uncommon to have an apple snail die of starvation, well before fish, as people often do not realize that they need to be fed specifically, just like any other intentional addition to your tank. There is a misconception that they can survive on algae alone similar to misconceptions that cories will just scavenge leftover food from the bottom.