Remove the TODO when increment zero

// If delta amount to apply is 0, don't write WAL or MemStore.
long deltaAmount = getLongValue(delta);
// TODO: Does zero value mean reset Cell? For example, the ttl.
apply = deltaAmount != 0;

// Give coprocessors a chance to update the new cell
if (coprocessorHost != null) {
  newCell =
      coprocessorHost.postMutationBeforeWAL(mutationType, mutation, currentValue, newCell);
}
// If apply, we need to update memstore/WAL with new value; add it toApply.
if (apply || firstWrite) {
  toApply.add(newCell);
}