Hoppers fail to suck item entities from above under certain conditions

Hoppers fail to suck item entities from above, if the first slot is occupied with a stack of the same item floating above them, and their cooldown counter is non-zero.

Steps to reproduce:

1. Place down a chest (or any other containers).
2. Connect a hopper to it.
3. Throw a stack of cobblestone (or any other items) onto it.
4. It sucks in the stack as expected, and its first slot is now occupied with the stack. All of the remaining 4 slots are still empty.
5. It starts to push the items into the container.
6. Throw in another stack of the same item before the hopper becomes empty.
7. Observe that the hopper doesn't suck in the second stack even though it has enough space to be filled up.
8. Throw in a stack of torches (or any other different items) before the hopper becomes empty.
9. Observe that the hopper successfully sucks in torches into its second slot.

This doesn't happen when the cooldown counter is zero, i.e. the hopper isn't pushing items into some other containers.

What I expect:
Hoppers should ignore the cooldown counter while trying to suck in item entities.