(svn r2156) -Fix: in revision 2104 someone forgot to add a very important check in

GetPrevVehicleInChain; this caused some nasty bugs in depots, like 
wagons without engines complain about not being stopped, and stuff like 
that. Hopefully this fixes those problems. With a big tnx to BJH for his 
perfect demo!

vehicle.c

@@ -358,7 +358,7 @@ Vehicle *GetPrevVehicleInChain(const Vehicle *v)
 {
 	Vehicle *u;
 
-	FOR_ALL_VEHICLES(u) if (u->next == v) return u;
+	FOR_ALL_VEHICLES(u) if (u->type == VEH_Train && u->next == v) return u;
 
 	return NULL;
 }