Sack disappears when trying to fill a partially full sack

What I did:

1. Take an empty sack and a few potatoes (say, 5).
2. Click on the sack to fill the sack with the potatoes. The sack is now partially full, but not completely.
3. Click on the sack again, which will do the fill action.

This also affects other vegetables, such as onions.

What I expected to happen: Nothing should happen, or some message should appear saying that you can't do that, or maybe the option shouldn't be available at all.

What actually happened: The sack and potatoes inside disappeared.

IDs of related NPCs/items: 5418-5439

2009-era source (if relevant): Not sure. I'll try to find something later.

Screenshots or video:

Screencast_from_2024-03-17_21-04-01

LIVE SERVER username affected by this issue: Raijin8

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