AttributeError: 'NoneType' object has no attribute 'next'

[loves]

The question is Given the head of a linked list, remove the nth node from the end of the list and return its head.

My code:

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

class Solution:
    def removeNthFromEnd(self, head: ListNode, n: int) -> ListNode:
        total = 0
        temp = head
        while temp is not None:
            temp = temp.next
            total += 1
          
        
        k = total - n
        prev = None
        curr = head
        while k > 0:
            prev.next = curr
            curr = curr.next
            k -= 1
        if prev is None:
            return head.next
        else:
            prev.next = curr.next
        return head
    
list1 = ListNode(2);
list1.next = ListNode(4)
list1.next.next = ListNode(3)
list1.next.next.next = ListNode(5);
list1.next.next.next.next = ListNode(6);
list1.next.next.next.next.next = ListNode(4)
list1.next.next.next.next.next.next = ListNode(7)
s = Solution()
print(s.removeNthFromEnd(list1, 5))

But I got the error at line 19

File "C:\Code\Leetcode-python\19.py", line 19, in removeNthFromEnd
prev.next = curr

AttributeError: 'NoneType' object has no attribute 'next'

Thanks for the hint.