Add documentation in OR manual

Author: Csantucci

Source/Documentation/Manual/sound.rst

@@ -430,6 +430,20 @@ Trigger       Function
 322           BoosterCylinderCocksClose
 =========     =====================================
 
+Following triggers referring to locomotive and train type are available:
+
+=========     =====================================
+Trigger       Function
+=========     =====================================
+330           AITrainLeadLoco
+331           AITrainHelperLoco
+332           PlayerTrainLeadLoco
+333           PlayerTrainHelperLoco
+334           AITrainApproachingStation
+335           AITrainLeavingStation
+=========     =====================================
+
+
 Variable Triggers
 -----------------
 

Source/RunActivity/Viewer3D/RollingStock/MSTSWagonViewer.cs

@@ -1470,7 +1470,7 @@ protected void LoadCarSound(string wagonFolderSlash, string filename)
                 }
                 else if (MSTSWagon == Viewer.PlayerLocomotive)
                     MSTSWagon.SignalEvent(Event.PlayerTrainLeadLoco);
-                else if (MSTSWagon.Train != null && (MSTSWagon.Train.TrainType == Train.TRAINTYPE.PLAYER ||
+                else if (MSTSWagon is MSTSLocomotive && MSTSWagon.Train != null && (MSTSWagon.Train.TrainType == Train.TRAINTYPE.PLAYER ||
                     MSTSWagon.Train.TrainType == Train.TRAINTYPE.AI_PLAYERDRIVEN || MSTSWagon.Train.TrainType == Train.TRAINTYPE.AI_PLAYERHOSTING))
                     MSTSWagon.SignalEvent(Event.PlayerTrainHelperLoco);
             }