Error when running the reference solution for Construct Binary Tree from Preorder and Inorder Traversal in Leetcode?

I'm looking at LeetCode problem: 105. Construct Binary Tree from Preorder and Inorder Traversal:

Given two integer arrays preorder and inorder where preorder is the preorder traversal of a binary tree and inorder is the inorder traversal of the same tree, construct and return the binary tree.

Template code:

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def buildTree(self, preorder: List[int], inorder: List[int]) -> Optional[TreeNode]:

I used the code that is provided in the Editorial of the challenge:

class Solution:
    def buildTree(self, preorder: List[int], inorder: List[int]) -> TreeNode:

        def array_to_tree(left, right):
            nonlocal preorder_index
            # if there are no elements to construct the tree
            if left > right: return None

            # select the preorder_index element as the root and increment it
            root_value = preorder[preorder_index]
            root = TreeNode(root_value)


            preorder_index += 1

            # build left and right subtree
            # excluding inorder_index_map[root_value] element because it's the root
            root.left = array_to_tree(left, inorder_index_map[root_value] - 1)
            root.right = array_to_tree(inorder_index_map[root_value] + 1, right)

            return root

        preorder_index = 0

        # build a hashmap to store value -> its index relations
        inorder_index_map = {}
        for index, value in enumerate(inorder):
            inorder_index_map[value] = index

        return array_to_tree(0, len(preorder) - 1)

Problem

My question is about running this test case:

preorder = [4,1,3,6,8]
inorder = [6,1,8,4,3]
tree = Solution().buildTree(preorder, inorder)

When running it, an exception occurs:

Traceback (most recent call last):
  File "main.py", line 43, in <module>
    tree = Solution().buildTree(preorder,inorder)
  File "main.py", line 30, in buildTree
    return array_to_tree(0, len(preorder) - 1)
  File "main.py", line 22, in array_to_tree
    root.left = array_to_tree(left, inorder_index_map[root_value] - 1)
  File "main.py", line 22, in array_to_tree
    root.left = array_to_tree(left, inorder_index_map[root_value] - 1)
  File "main.py", line 22, in array_to_tree
    root.left = array_to_tree(left, inorder_index_map[root_value] - 1)
  File "main.py", line 23, in array_to_tree
    root.right = array_to_tree(inorder_index_map[root_value] + 1, right)
  File "main.py", line 22, in array_to_tree
    root.left = array_to_tree(left, inorder_index_map[root_value] - 1)
  File "main.py", line 19, in array_to_tree
    root_value = preorder[preorder_index]
IndexError: list index out of range

Analysis

The following is my manual calculation:

The tree should look like this:

    4
   / \
  1   3
 / \
6   8

Hand Calculating:

preorder = [4, 1, 3, 6, 8]
hashmap: {6:0 ; 1:1 ; 8:2 ; 4:3 ; 3:4 }
preorderindex = 0

loop 1:

  left = 0 right = 3
  preorderindex = 0 => root value = 4 => new right = 2
  tree: 

    4

loop 2:

  left = 0 right = 2
  preorderindex = 1 => root value = 1 => new right = 0
  tree: 

      4
     /
    1

loop 3:

  left =0 right = 0
  preorderindex = 2 => root value = 3 => new right = 3
  tree:

       4
      /
     1
    /
   3

At this step, there is already an error, and I really wonder where is the mistake?

I'm so confused, I don't believe there is a mistake in this code, but then I can't figure out where is my mistake?