Medium Trade bug with "one of a kind item"

Description of the bug:
Trading a "one of a kind item" to another player that already has the item will make the instance of the item traded disappear.

(optional screenshot/video): https://www.youtube.com/watch?v=5XteN1z43n4

What is supposed to happen?:
The trade should be cancelled if the player already has the item, like it does when trying to buy the same item in the Free Market, as shown in the video.

Where did you find and/or notice this bug?:
I obtained a frozen book of ice from hunting monsters and wanted to trade it with my other character. I noticed that my other character already had the frozen book of ice but I wanted to try trading it anyway.

A step-by-step guide to re-producing this bug (optional):

1. Obtain a "one of a kind item" on one character.
2. Obtain another instance of the same item on a different character.
3. Trade the item on one of the two characters to the other character.

Extra information (optional):
Frozen Book of Ice isn't an expensive item, but there is probably another that is more valuable that could potentially be lost forever so I will list this as medium.