Refine loading code - Githubissues

Some small updates at the loading code comments / variable names.

The null TODO needs to be answered, then it can be an PR to "real" main

[ ] Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)
[ ] Tests created for changes (if applicable)
[ ] Manually tested changed features in running JabRef (always required)
[ ] Screenshots added in PR description (for UI changes)
[ ] Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.
[ ] Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

koppor / jabref