Merge pull request #1059 from mbm-OR/bugfix/Fix-F9-powersupply-crashes

Fix F9 powersupply crashes

Author: mbm-OR

Source/RunActivity/Viewer3D/Popups/TrainCarOperationsWindow.cs

@@ -690,13 +690,14 @@ public override void PrepareFrame(ElapsedTime elapsedTime, bool updateFull)
                 // Updates power supply status
                 else if (SelectedCarPosition <= CarPositionVisible && SelectedCarPosition == CarPosition)
                 {
-                    var powerSupplyStatusChanged = PowerSupplyStatus != null && PowerSupplyStatus != Owner.Viewer.PlayerTrain.Cars[CarPosition].GetStatus();
-                    var batteyStatusChanged = BatteryStatus != null && BatteryStatus != Owner.Viewer.PlayerTrain.Cars[CarPosition].GetStatus();
-                    var circuitBreakerStateChanged = CircuitBreakerState != null && CircuitBreakerState != (Owner.Viewer.PlayerTrain.Cars[CarPosition] as MSTSElectricLocomotive).ElectricPowerSupply.CircuitBreaker.State.ToString();
+                    var carposition = Owner.Viewer.PlayerTrain.Cars.Count > CarPosition ? CarPosition : CarPosition - 1;
+                    var powerSupplyStatusChanged = PowerSupplyStatus != null && PowerSupplyStatus != Owner.Viewer.PlayerTrain.Cars[carposition].GetStatus();
+                    var batteyStatusChanged = BatteryStatus != null && BatteryStatus != Owner.Viewer.PlayerTrain.Cars[carposition].GetStatus();
+                    var circuitBreakerStateChanged = CircuitBreakerState != null && CircuitBreakerState != (Owner.Viewer.PlayerTrain.Cars[carposition] as MSTSElectricLocomotive).ElectricPowerSupply.CircuitBreaker.State.ToString();
 
                     if (powerSupplyStatusChanged || batteyStatusChanged || circuitBreakerStateChanged)
                     {
-                        var Status = Owner.Viewer.PlayerTrain.Cars[CarPosition].GetStatus();
+                        var Status = Owner.Viewer.PlayerTrain.Cars[carposition].GetStatus();
                         if (Status != null && Status != PowerSupplyStatus)
                         {
                             PowerSupplyStatus = Status;