Webform composite elements not exportable via webform_xlsx_export module

Problem/Motivation

When I create a webform with predefined composite fields like "Telephone advanced" or "Address" or "Webform workflows element" and I have the module "webform_xlsx_export" installed I get an error in my excel file saying:
<b>Notice</b>: Undefined index: #type in <b>/var/www/web/modules/contrib/webform/src/Plugin/WebformElement/WebformCompositeBase.php</b> on line <b>799</b><br />

And then the excel file needs to be repaired which results in data loss or a file that cannot be opened.

Steps to reproduce

1. Create a drupal project and install the module "webform_xlsx_export"
2. Create a webform with for example an address field (other possibilities are the telephone_advanced field or webform workflow element)
3. Create a couple submissions for the form
4. Go to the results and try to export the submissions as a .xlsx file

Proposed resolution

I added a small patch which just makes it so I can export my submissions but I don't consider it a fix.

Remaining tasks

Make it so the webform_xlsx_export module can also export these composite fields.

User interface changes

API changes

Data model changes