avoid trying to removing the same disabled gears over and over again (which...

avoid trying to removing the same disabled gears over and over again (which leads to an error because an already disabled gear cannot be disabled twice).
remove disabled gears on a clone of the gear  list provided by the input provider

VectoCore/VectoCore/InputData/Reader/DataObjectAdapter/DeclarationDataAdapter.cs

@@ -236,7 +236,8 @@ namespace TUGraz.VectoCore.InputData.Reader.DataObjectAdapter
 			retVal.Inertia = DeclarationData.Engine.EngineInertia(retVal.Displacement, gearbox.Type);
 			retVal.EngineStartTime = DeclarationData.Engine.DefaultEngineStartTime;
 			var limits = vehicle.TorqueLimits.ToDictionary(e => e.Gear);
-			var gears = FilterDisabledGears(gearbox.Gears, limits);
+			var gearsCopy = new List<ITransmissionInputData>(gearbox.Gears);
+			var gears = FilterDisabledGears(gearsCopy, limits);
 			var numGears = gears.Count;
 			var fullLoadCurves = new Dictionary<uint, EngineFullLoadCurve>(numGears + 1);
 			fullLoadCurves[0] = FullLoadCurveReader.Create(mode.FullLoadCurve, true);
@@ -336,7 +337,8 @@ namespace TUGraz.VectoCore.InputData.Reader.DataObjectAdapter
 			}
 
 			var limits = inputData.TorqueLimits?.ToDictionary(e => e.Gear) ?? new Dictionary<int, ITorqueLimitInputData>();
-			var gearsInput = FilterDisabledGears(gearbox.Gears, limits);
+			var gearscopy = new List<ITransmissionInputData>(gearbox.Gears);
+			var gearsInput = FilterDisabledGears(gearscopy, limits);
 			if (gearsInput.Count < 1) {
 				throw new VectoSimulationException(
 					"At least one Gear-Entry must be defined in Gearbox!");