Fix +10%/-10% fuel buttons in station's lobby

Updated to fix mixed up behaviour of decreasing in stock and demand of station's goods using +10%/-10% fuel buttons(-10% decreases in stock and +10% decreases demand).

data/pigui/modules/station-view/01-lobby.lua

@@ -129,7 +129,7 @@ local refuelInternalTank = function (delta)
 
 	Game.player:AddMoney(-total)
 	local commodityChangeAmount = mass < 0 and math.floor(mass) or math.ceil(mass)
-	station:AddCommodityStock(Commodities.hydrogen, commodityChangeAmount)
+	station:AddCommodityStock(Commodities.hydrogen, -commodityChangeAmount)
 	Game.player:SetFuelPercent(fuel)
 end