合并排序链表出现分割错误

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

def mergeTwoLists(l1, l2):
    if not l1:
        return l2
    if not l2:
        return l1
    if l1.val <= l2.val:
        l1.next = mergeTwoLists(l1.next, l2)
        return l1
    else:
        l2.next = mergeTwoLists(l1, l2.next)
        return l2

# 示例用法
# 创建链表1: 1 -> 3 -> 5
l1 = ListNode(1)
l1.next = ListNode(3)
l1.next.next = ListNode(5)

# 创建链表2: 2 -> 4 -> 6
l2 = ListNode(2)
l2.next = ListNode(4)
l2.next.next = ListNode(6)

# 合并两个有序链表
merged_list = mergeTwoLists(l1, l2)

# 打印合并后的链表: 1 -> 2 -> 3 -> 4 -> 5 -> 6
while merged_list:
    print(merged_list.val, end=" -> ")
    merged_list = merged_list.next
print("None")