Stall incorrectly handles multiples of ingots traded

[TheWhiteWolves]

While having a play around with your mod and testing it out I found that the stall is incorrectly handling the trading of multiple ingots in a trade.

[Warehaouse and Ingot piles before the trade]

[Stall GUI before the trade]

[Stall GUI after trading 2 iron for 1 gold - this works correctly as expected]

[The warehouse and ingot piles after the first trade]

[The Stall GUI after trading 1 gold for 2 iron - it looks like it worked as expected, However...]

[After closing and reopening the GUI - notice it the numbers are not what they should be...]

[The ingot piles show that it has only taken 1 of the 2 iron away in the second trade and given 2 iron to the buyer and has taken 1 gold from the buyer but not given it to the seller]

Hope this is enough for you to understand whats happening and maybe track down the cause.

[TheWhiteWolves]

Also to note I was using Forge-10.13.2.1264, TerraFirmaCraft-0.79.13.468 and Merchants-1.0.8.

[Aleksey-Terzi]

Thank you for detailed description.
Bug is reproduced and fixed in 1.0.10