LeetCode刷题：runtime error: reference binding to null pointer of type 'int' (stl_vector.h)报错请教

题目：https://leetcode.cn/problems/merge-intervals/
错误代码：

// 思路初探：做了很多道类似区间操作的题目了。本题就是尽可能少的创建新区间
// 1.首先对区间排序（左边界升序，右边界都行）
// 2.遍历合并
class Solution {
public:
    static bool myCmp(vector<int> a,vector<int> b){
        return a[0] <= b[0];
    }
    vector<vector<int>> merge(vector<vector<int>>& intervals) {
        vector<vector<int>> res;
        if (intervals.size() == 0) return res;
        sort(intervals.begin(),intervals.end(),myCmp);
        int lastRight = intervals[0][1];
        int lastLeft = intervals[0][0];
        for(int i = 1; i < intervals.size();i++){
            int curLeft = intervals[i][0];
            int curRight = intervals[i][1];
            if(curLeft > lastRight){
                //创建新区间
                res.push_back(vector<int>{lastLeft,lastRight});
                lastLeft = curLeft;
                lastRight = curRight;
            }else{ //延长原来的区间
                lastRight = max(lastRight,curRight);
            }
        }
        res.push_back(vector<int>{lastLeft,lastRight});
        return res;
    }
};

报错提示：

Line 1034: Char 9: runtime error: reference binding to null pointer of type 'int' (stl_vector.h)
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/stl_vector.h:1043:9