Some empty entries are not filtered

[thomas-saigre]

When exporting Zotero library to bibtex file, some empty entries are added to the file.
A first filter is done for empty ones, but some of them are empty but still contain a keywords entry :

@misc{noauthor_notitle_nodate-25,
	keywords = {laser, output},
}

@misc{noauthor_notitle_nodate-26,
	keywords = {laser, laserParam},
}

@misc{noauthor_notitle_nodate-27,
	keywords = {laser, laserParam},
}