Items are lost when disconnecting during a money/XP offer

[sh1mrr4]

Hello,

A few players on my server reported that items offered in a trade are lost, if a player loses the connection while entering a number for XP/money.

Steps to reproduce the issue:

• Trade with somebody
• Add an item to the trade
• Click the money/XP offer button
• Disconnect
  (only the items of the disconnecting player are lost)

Trade+ Version: 3.79 (tested 3.76.1 as well)
Server version: Paper 1.15-378

It would be great if you could have a look at this and possibly fix it. Please let me know if you need more information or anything else to reproduce the issue.