c语言数据结构队列问题，出现nullptr，请问是哪里有问题呢

Question

typedef int quint;
typedef struct qnode{
    quint data;
    struct qnode* next;
}qnode;

typedef struct qu {
    qnode * head;
    qnode* tail;
}qu;

void intqu(qu *q) {
    if(q == NULL)
    {
        exit(-1);
    }
    
        q->head = NULL;
        q->tail = NULL;
    
}

void pushqu(qu* q, quint x) {
    qnode* newnode = (qnode*)malloc(sizeof(qnode)); 
    if (newnode == NULL) {
        printf("内存分配不成功！\n");
    }
    else {
        newnode->data = x;
        newnode->next = NULL;
    }
        if (q->head == NULL) {
            q->head = q->tail = newnode;
        }
        else {
            q->tail->next = newnode;
            q->tail = newnode;
        }
    }


void popqu(qu* q) {
    if (q->head == NULL) {
        printf("删除失败，队列空");
    }
    else {
        qnode* tem = q->head->next;
        q->head = NULL;
        free(q->head);
        q->head = tem;
        if (q->head = NULL)
        {
            q->tail = NULL;
        }
    }
}

quint QueueFront(qu* qu)
{
    if (qu == NULL)
        return 0;
    else
    return qu->head->data;
};
quint QueueBack(qu* qu)
{
    if (qu == NULL)
        return 0;
    else
    return qu->tail->data;
};
int main() {
    qu q;
    intqu(&q);
    pushqu(&q, 1);
    pushqu(&q, 2);
    popqu(&q);//这里报错，说引发了异常: 读取访问权限冲突。q.head 是 nullptr。
    printf("%d", q.head->data);
    return 0;
    
}

Answer 1

52行改为if (q->head == NULL)