Resolve "Data op `create_mask` fails if data.name is `None"

This MR fixes data operations errors for data.name is None in count_unique and create_mask.

To double check

Do we want a test, that it actually works? I've run it successfully against the function where it occurred.

Can this MR be accepted?

• Implementation ready
• Tests added or adjusted
• Documentation extended or updated

• Code quality
  • Changes follow coding guidelines
  • Checked code coverage on new and adjusted code

• Ready for merging
  • Pipeline passes without warnings
  • History cleaned-up or squash option set
  • Changelog entry added
  • Version number bumped
  • Reviewed & approved by @blsqr

Related issues

Closes #203 (closed)