(svn r15354) -Fix (r14803): first shared of a vehicle could be NULL making it impossible to (share-)clone the vehicle.

src/order_cmd.cpp

@@ -1427,9 +1427,8 @@ void CheckOrders(const Vehicle *v)
 		/* Do we only have 1 station in our order list? */
 		if (n_st < 2 && problem_type == -1) problem_type = 0;
 
-		assert(v->orders.list); // otherwise the check for v->FirstShared() != v would have been true
 #ifndef NDEBUG
-		v->orders.list->DebugCheckSanity();
+		if (v->orders.list != NULL) v->orders.list->DebugCheckSanity();
 #endif
 
 		/* We don't have a problem */

src/vehicle_base.h

@@ -515,7 +515,7 @@ public:
 	 * Get the first vehicle of this vehicle chain.
 	 * @return the first vehicle of the chain.
 	 */
-	inline Vehicle *FirstShared() const { return (this->orders.list == NULL) ? NULL : this->orders.list->GetFirstSharedVehicle(); }
+	inline Vehicle *FirstShared() const { return (this->orders.list == NULL) ? this->First() : this->orders.list->GetFirstSharedVehicle(); }
 
 	/**
 	 * Check if we share our orders with another vehicle.