Quantity in the new trade/inventory UI doesn't clear properly

[tripdrake]

When trading with any merchant, interacting with a container, etc and setting the quantity to be moved with the keyboard, the number traded will not clear unless you keyboard up to another item after deselecting it, and it can’t be changed at that point by entering another quantity.

Expected behavior is that when pressing enter again to deselect the item, the quantity entered would be cleared, or that using backspace, or entering a new quantity would reset the field.

I believe that was the original behavior before the spring molting update.

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