How to get DF from XML using read_xml() and xpath(2)?

Question

Could you please help me parse the following XML? NaN is not handled properly. Previous question: How to get DF from XML using read_xml() and xpath?

import pandas as pd
from io import StringIO # StringIO

xml = '''<?xml version="1.0" encoding="UTF-8" ?>
    <vector result="5">
        <data vectorkey="0" type="Document">
            <result><RGT_STD_DT value="20231101"/><TH1_PAY_TERM_BEGIN_DT value=""/><SHOTN_ISIN value="183190"/><ISSUCO_CUSTNO value="21505"/></result>
        </data>
        <data vectorkey="1" type="Document">
            <result><RGT_STD_DT value="20231031"/><TH1_PAY_TERM_BEGIN_DT value=""/><SHOTN_ISIN value="448730"/><ISSUCO_CUSTNO value="48052"/></result>
        </data>
        <data vectorkey="2" type="Document">
            <result><RGT_STD_DT value="20231031"/><TH1_PAY_TERM_BEGIN_DT value=""/><SHOTN_ISIN value="453440"/><ISSUCO_CUSTNO value="48543"/></result>
        </data>
        <data vectorkey="3" type="Document">
            <result><RGT_STD_DT value="20231005"/><TH1_PAY_TERM_BEGIN_DT value="20231025"/><SHOTN_ISIN value="009970"/><ISSUCO_CUSTNO value="997"/></result>
        </data>
        <data vectorkey="4" type="Document">
            <result><RGT_STD_DT value="20231004"/><TH1_PAY_TERM_BEGIN_DT value="20231018"/><SHOTN_ISIN value="078520"/><ISSUCO_CUSTNO value="9602"/></result>
        </data>
    </vector>'''

df = pd.read_xml(StringIO(xml), xpath='//*[local-name()="result"]/*')
print(df)

df2 = []
i = 0
while (i < len(df.index)):
    tdf = df[i:i+4]
    tdf = tdf.transpose()
    tdf.columns = ["RGT_STD_DT", "TH1_PAY_TERM_BEGIN_DT", "SHOTN_ISIN", "ISSUCO_CUSTNO"]
    df2.append(tdf)
    i = i + 4
print(pd.concat(df2))

D:\Temp\python xml_to_df.py
       value
0   20231101
1     183190
2      21505
3   20231031
4     448730
5      48052
6   20231031
7     453440
8      48543
9   20231005
10  20231025
11      9970
12       997
13  20231004
14  20231018
15     78520
16      9602
Traceback (most recent call last):
  File "D:\Temp\xml_to_df.py", line 35, in make_dividend_from_seibro
    tdf.columns = ["RGT_STD_DT", "TH1_PAY_TERM_BEGIN_DT", "SHOTN_ISIN", "ISSUCO_CUSTNO"]
    ^^^^^^^^^^^
...
  File "C:\Users\gmde0\AppData\Local\Programs\Python\Python311\Lib\site-packages\pandas\core\internals\base.py", line 70, in _validate_set_axis
    raise ValueError(
ValueError: Length mismatch: Expected axis has 1 elements, new values have 4 elements