C++ 未经处理的异常: 将一个无效参数传递给了将无效参数视为严重错误的函数

0x0FA5E636 (ucrtbased.dll) (set.exe 中)处有未经处理的异常: 将一个无效参数传递给了将无效参数视为严重错误的函数。 这是哪里错了

 #include<iostream>
#include<set>
#include<vector>
#include<string>
using namespace std;
string find_book(vector<string> & abooklist, set<string> &abooks);
int main()
{
    vector <string> booklist;// the books I wanna read
    booklist.push_back("a");
    booklist.push_back("b");
    booklist.push_back("c");

    set<string> books;//the books I have read
    books.insert("a");
    books.insert("c");
    books.insert("x");
    books.insert("g");

    cout<<"the book for you : "<<find_book(booklist, books)<<endl;
    getchar();
    return 0;
}

string find_book( vector<string> & abooklist, set<string> &abooks )
{
    //find a book from booklist that can not be found in books
    vector<string>::iterator iter = abooklist.begin();
    while (iter != (abooklist.end()))
    {
        if (!abooks.count(*iter))
        {
            string temp=*iter;
            abooks.insert(*iter);
            abooklist.erase(iter);//remove the book found int booklist 
                                                                            //and put it in books
            return temp;
        }

        iter++;
    }
    return "not found";
}