TypeError: int() argument must be a string, a bytes-like object or a real number, not 'NoneType'

[rizaumami]

On offline machine, I did:

sudo apt-offline set offline.sig --update --upgrade

Then, on online machine I did:

sudo apt-offline get offline.sig --bundle offline.zip

But, unable to get updated packages because of error:

Exception in thread Thread-1 (run):#############] 100.0% of 38 MiB
Traceback (most recent call last):
  File "/usr/lib/python3.13/threading.py", line 1043, in _bootstrap_inner
    self.run()
    ~~~~~~~~^^
  File "/usr/lib/python3.13/threading.py", line 994, in run
    self._target(*self._args, **self._kwargs)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/apt_offline_core/AptOfflineLib.py", line 741, in run
    self.responseQueue.put(self.WorkerFunction(item, thread_name))
                           ~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/apt_offline_core/AptOfflineCoreLib.py", line 1682, in DataFetcher
    if DownloadPackages(NewUrl, NewPackageFile) is True:
       ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/apt_offline_core/AptOfflineCoreLib.py", line 1606, in DownloadPackages
    if FetcherInstance.download_from_web(
       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
        PackageName, PackageFile, Str_DownloadDir
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    ):
    ^
  File "/usr/lib/python3/dist-packages/apt_offline_core/AptOfflineCoreLib.py", line 839, in download_from_web
    size = int(headers["Content-Length"])
TypeError: int() argument must be a string, a bytes-like object or a real number, not 'NoneType'