C++矢量下标超出范围

据我所知，这个错误通常发生在迭代器越界时，但我在空向量上遇到了这个问题。

这是保存矢量的Player类：

Player.h:

#pragma once
#include "Item.h"
#include "Room.h"
#include <vector>
#include <memory>
#include <string>
using namespace std;
class Player
{
private:
    int health;
    string name;
    shared_ptr<Room> currentRoom;
    vector<shared_ptr<Item> > inventory;
public:
    Player(void);
    Player(string);
    ~Player(void);
    void changeHealth(int);
    void setRoom(shared_ptr<Room>);
    shared_ptr<Room> getRoom();
    unsigned int getInventorySize();
};

Player.cpp:

#include "Player.h"
#include <iostream>
#include <memory>
#include <string>
Player::Player(void)
{
    health = 20;
}
Player::Player(string newName)
{
    name = newName;
}
Player::~Player(void)
{
}
void Player::changeHealth(int amount){
    health += amount;
}
void Player::setRoom(shared_ptr<Room> newRoom){
    currentRoom = newRoom;
}
shared_ptr<Room> Player::getRoom(){
    return currentRoom;
}
unsigned int Player::getInventorySize(){
    return inventory.size();
}

我评论掉了Player中影响库存的所有其他方法。总的来说，我制作了一个播放器对象，但我不做任何库存操作，所以它应该是完全空的，getInventorySize应该返回0，对吧？但当我这样做时：

cout<<player->getInventorySize();

程序因矢量下标超出范围错误而崩溃。发生了什么事

完整主干：

#include "World.h"
#include "Player.h"
#include "Room.h"
#include "Item.h"
#include "Option.h"
#include "RoomOption.h"
#include <iostream>
#include <memory>
#include <string>
#include <stdlib.h>
typedef shared_ptr<Option> optionPtr;
typedef shared_ptr<Item> itemPtr;
typedef shared_ptr<Room> roomPtr;
const int healthPackID =0;
World world;
void createWorld(void);
void main(){
    createWorld();
    shared_ptr<Player> player = world.getPlayer();
    int selection = 0, inventoryOption = 0, exitOption = 0;
    do{
        inventoryOption = player->getRoom()->getNumOptions() + 1;
        exitOption = inventoryOption + 1;
        cout<<player->getRoom()->getDescription()<<endl;
        player->getRoom()->printOptions();
        cout<< inventoryOption <<". View Inventory"<<endl;
        cout<< exitOption <<". Quit game"<<endl<<endl;
        cin>>selection;
        string optionType = typeid(*(player->getRoom()->getOption(selection-    1).get())).name();
        if(selection == inventoryOption){
            cout<<player->getInventorySize();
        }
        else if( optionType.compare("class RoomOption") == 0){
            player->setRoom(player->getRoom()->getOption(selection-    1)->getRoom());
            cout<< "RoomOption!"<<endl;
        }
        else{
            cout<< "Not RoomOption =("<<endl;
        }
        system("CLS");
    }while(selection != exitOption);
}
void createWorld(){

    shared_ptr<Player> player(new Player("Ted"));
    world.setPlayer(player);
    roomPtr outside(new Room(0, "You're outside", ""));
    roomPtr hallway(new Room(1, "It's a hallway", ""));
    roomPtr kitchen(new Room(2, "It's the kitchen", ""));
    roomPtr livingRoom(new Room(3, "You're in the living room", ""));
    roomPtr upstairs(new Room(4, "You're on the upstairs landing but all the doors are     barred shut", ""));

    outside->addOption(optionPtr(new RoomOption(0, "Go inside", hallway)));
    hallway->addOption(optionPtr(new RoomOption(0, "Go straight ahead into the     kitchen", kitchen)));
    hallway->addOption(optionPtr(new RoomOption(1, "Go right into the living     room", livingRoom)));
    hallway->addOption(optionPtr(new RoomOption(2, "Go upstairs", upstairs)));
    hallway->addOption(optionPtr(new RoomOption(3, "Go back outside", outside)));
    hallway->addItem(itemPtr(new Item(healthPackID, "Health Pack", "A pack full of     first aid items like bandages and surgical spirits. Use it to increase your health", 3)));
    kitchen->addOption(optionPtr(new RoomOption(0, "Go right into the living     room", livingRoom)));
    kitchen->addOption(optionPtr(new RoomOption(1, "Go back into the hallway",     hallway)));
    kitchen->addItem(itemPtr(new Item(1, "Cake", "A piece of tasty cake", 1)));
    kitchen->addItem(itemPtr(new Item(2, "Beer", "A cold bottle of generic brand     beer", 1)));
    livingRoom->addOption(optionPtr(new RoomOption(0, "Go left into the kitchen",     kitchen)));
    livingRoom->addOption(optionPtr(new RoomOption(1, "Go back into the     hallway",hallway)));
    upstairs->addOption(optionPtr(new RoomOption(0, "Go back downstairs", hallway)));
    world.addRoom(outside);
    world.addRoom(kitchen);
    world.addRoom(livingRoom);
    world.addRoom(hallway);
    world.addRoom(upstairs);
    player->setRoom(outside);

}