Core/Entities: Send SMSG_DISMOUNT notification to client when dismounting (mount/vehicle).

Thanks to Vladimir.

src/server/game/Entities/Unit/Unit.cpp

@@ -11657,6 +11657,10 @@ void Unit::Unmount()
     SetUInt32Value(UNIT_FIELD_MOUNTDISPLAYID, 0);
     RemoveFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_MOUNT);
 
+    WorldPacket data(SMSG_DISMOUNT, 8);
+    data << GetPackGUID();
+    SendMessageToSet(&data, true);
+
     // only resummon old pet if the player is already added to a map
     // this prevents adding a pet to a not created map which would otherwise cause a crash
     // (it could probably happen when logging in after a previous crash)