단일연결리스트 에서 전체리스트를 삭제하는 함수인데 에러가뜨네요...

#include <stdio.h>
#include <stdlib.h>
 
typedef struct ListNode{
 
	int data;
	struct ListNode *link;
 
} ListNode;
 
void init(ListNode *head) {
 
	head->data = 0;
	head->link = NULL;	
}
 
void add(ListNode *head, int item) {
 
	ListNode *newNode;
	newNode = (ListNode*)malloc(sizeof(ListNode));
 
	newNode->data = item;
	newNode->link = head->link;
	head->link = newNode;
}
 
void delete(ListNode *head, int item) {
 
	ListNode* cur = head;
	ListNode* deleteNode;
	int isRun = 0;
 
	while (cur->link != NULL) {
		if (cur->link->data == item) {
			isRun = 1;
			deleteNode = cur->link;
			cur->link = deleteNode->link;
			free(deleteNode);
			break;
		}
		cur = cur->link;
	}
	if (isRun == 0)
		printf("delete error: item %d값이 없습니다.\n", item);
}
 
void find(ListNode *head, int item) {
 
	int isRun = 0;
	ListNode *findNode = head;
 
 
	while (findNode != NULL) {
		if (findNode->data == item) {
			isRun = 1;
			return findNode;
		}
		findNode = findNode->link;
	}
	if (isRun == 0)
		printf("find error: item %d값이 없습니다.\n", item);
}
 
int length(ListNode *head) {
 
	ListNode *current = head;
	int count = 0;
 
	while (!isempty(current)) {
		current = current->link;
		count++;
	}
	printf("%d\n", count-1);
	return (count-1);
}
 
void destroy(ListNode *head) {
 
	ListNode *current = head;
	ListNode *temp;
 
	while (current != NULL) {
		temp = current;
		current = current->link;
		free(temp);
	}
}
 
int isempty(ListNode *head) {
	return head == NULL;
}
 
void display(ListNode *head) {
 
	ListNode *p = head->link;
 
	while (p != NULL) {
		printf("%d -> ", p->data);
		p = p->link;
	}
	printf("\n");
}
 
int main() {
 
	ListNode *list1;
	list1 = (ListNode *)malloc(sizeof(ListNode));
 
	init(list1);
	add(list1, 3);
	add(list1, 4);
	add(list1, 1);
 
	find(list1, 6);
 
	delete(list1, 2);
 
	length(list1);
 
 
	destroy(&list1);
	display(list1);
 
 
 
	free(list1);
 
	system("pause");
	return 0;
 
}