immobile_builder: Get just the last command. (#4018)

Get just the last command.

luaui/Widgets/unit_immobile_builder.lua

@@ -34,6 +34,7 @@ local spGetUnitPosition		= Spring.GetUnitPosition
 local spGiveOrderToUnit		= Spring.GiveOrderToUnit
 local spGetCommandQueue     = Spring.GetCommandQueue
 local spGetSpectatingState	= Spring.GetSpectatingState
+local spGetUnitCurrentCommand   = Spring.GetUnitCurrentCommand
 
 local hmsx = Game.mapSizeX/2
 local hmsz = Game.mapSizeZ/2
@@ -132,10 +133,13 @@ end
 
 function widget:UnitCommand(unitID, unitDefID, _, cmdID, _, cmdOpts)
 	if isImmobileBuilder[unitDefID] and cmdOpts.shift and cmdID ~= CMD_FIGHT then
-		local commandQueue = spGetCommandQueue(unitID, -1)
-		local lastCommand = commandQueue[#commandQueue]
-		if lastCommand and lastCommand.id == CMD_FIGHT then
-			spGiveOrderToUnit(unitID, CMD.REMOVE, { lastCommand.tag }, 0)
+		local count = spGetCommandQueue(unitID, 0)
+		if count == 0 then
+			return
+		end
+		local cmdID, opts, tag = spGetUnitCurrentCommand(unitID, count)
+		if cmdID and cmdID == CMD_FIGHT then
+			spGiveOrderToUnit(unitID, CMD.REMOVE, { tag }, 0)
 		end
 	end
 end