System.ArgumentOutOfRangeException at Orts.Simulation.RollingStocks.SubSystems.Controllers.MSTSNotchController.SetPercent (U2023.05.06-0707, Marias Pass, ITR_e1_s1_w1_t1, Crash When Controlling Throttleless Units via Raildriver)

[Phillip Schlichting]

When the player is in control of a locomotive with no throttle in the engine file (a locomotive such as a B unit), using a raildriver to control the throttle will crash the sim.

To reproduce:
1. Find or create a locomotive that can be selected by the player, but has no throttle defined in the .eng file. I did this by creating a copy of the MSTS Dash 9 as TRAINS\TRAINSET\DASH9\OpenRails\dash9.eng and deleting the whole 'EngineControllers' section.
2. Start any activity with the locomotive in question.
3. Verify that the throttle is nonfunctional by attempting to adjust the throttle via keyboard.
4. Activate a connected raildriver controller.
5. Move the throttle on the raildriver to full.
6. The sim will crash reporting a System.ArgumentOutOfRangeException related to Orts.Simulation.RollingStocks.SubSystems.Controllers.MSTSNotchController.SetPercent(Single percent)

While controls other than the throttle may be missing from a B unit, using a raildriver to move those controls doesn't cause a crash. Using the dynamic brake, automatic brake, or independent brake levers has no effect. Most other controls work as usual, even if EngineControllers is missing.