Villager Trading broken - All trades require 2 slots

Villagers with trades that require only one input show 2 trade input slots. This results in trades not working, if they only required one input. Screenshot attached.

Examples:

• Farmer Melon to Emerald trade

• Librarian Emerald to Glass trade

I have tested providing the input material in the first or second slot, as well as providing the input in both slots. Trades are not working with all combinations.

Trades requiring two inputs (e.g. Librarian book trades) are unaffected and work as intended.