clean bibtex file

[thomas-saigre]

When running ./a.cli update-bibtex, it could happen that many empty entries are included in the generated bib file, e.g.

@article{sadeghi_mathematical_2024,
	title = {Mathematical {Models} of {Ocular} {Drug} {Delivery}},
	volume = {65},
	copyright = {http://creativecommons.org/licenses/by-nc-nd/4.0/},
	issn = {1552-5783},
	url = {https://iovs.arvojournals.org/article.aspx?articleid=2800804},
	doi = {10.1167/iovs.65.11.28},
	language = {en},
	number = {11},
	journal = {Investigative Ophthalmology \& Visual Science},
	author = {Sadeghi, Amir and Subrizi, Astrid and Del Amo, Eva M. and Urtti, Arto},
	month = sep,
	year = {2024},
	note = {Publisher: Association for Research in Vision and Ophthalmology (ARVO)},
	pages = {28},
}

@misc{noauthor_notitle_nodate,
}

@misc{noauthor_notitle_nodate-1,
}

@misc{noauthor_notitle_nodate-2,
}

It seems to be an error related to Zotero API, as other services have the same behavior (see for instance typst/webapp-issues#489 or https://forums.zotero.org/discussion/97526/duplicated-noauthor-nodate-entries).

With the modifications of the PR, after generating the bibtex, all empty entries are deleted using a regexp.