You can eat overcooked rice but overcooked rice is harder for your stomach to digest and metabolize.
There's no harm in eating overcooked rice though but if you don't want to eat the overcooked rice directly you can turn the overcooked rice into fritters, cakes, veggie burgers or add it to soups or even make it into porridge.
If the overcooked rice has become burnt though it's usually best to throw it out since it can contain carcinogenic substances that are cancer causing chemicals.
But if the rice is just overcooked and not burnt it's still safe to eat.