PathProperties._from_generated raises exception if last_modified is empty

[blem14]

• Package Name: azure-storage-file-datalake
• Package Version: 12.6.0
• Operating System: Windows 11 x64
• Python Version: 3.9.7

Describe the bug
Listing paths may fail on directories with empty last_modified.
Introduced in PR #16093.

To Reproduce
Steps to reproduce the behavior:

1. Have directory/file in the datalake without last_modified filled.
2. Run

   from azure.storage.filedatalake import DataLakeServiceClient
   service_client = DataLakeServiceClient(url, credential)
   fs_client = service_client.get_file_system_client(file_system)
   for p in fs_client.get_paths():
       print(p.name)

3. Get TypeError: strptime() argument 1 must be str, not None at azure/storage/filedatalake/_models.py:224.

Expected behavior
Listing directories not failing on directories/files with empty last_modified.
If last_modified can't be cast to datetime.datetime, it should be None.

Additional context
Not sure how last_modified ended up being empty in the first place, but I've met with such case on client's datalake.

[l0lawrence]

Thanks for the feedback, we'll investigate this asap.

[jalauzon-msft]

Hi @blem14, thanks for reporting this and doing a bit of investigation to figure out the issue! I'm also not really sure how a file/directory would end up with no last_modified time from the server, that seems odd. Either way, this does seem like a case we should handle. I'm making changes in this area for the upcoming release, I'll go ahead and fix it there as well.

[jalauzon-msft]

This has been merged and will be part of our upcoming release.