Add fixes to overcome errors when datasets are empty

[davide-f]

Closes # (if applicable).

Change proposed in this Pull Request

While executing the code for general non-EU zones, sometimes empty dataframes were returned leading to issues because of missing columns and similar problems.
In this PR, we aimed at solving some of those that have been encountered.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Other

Checklist

• I have added a note to release notes doc/release_notes.rst.
• I have used pre-commit run --all to lint/format/check my contribution
• I have documented the effects of my code changes in the documentation doc/.
• I have adjusted the docstrings in the code appropriately.

[FabianHofmann]

great thanks @davide-f