Obscure error message if .bib file left unspecified

I kept getting an obsure error message every time Joplin started up which was something like (can't find exact message):

"error could not open some files: ENOENT: no such file or directory"

I narrowed down the problem to this plugin, and the fact I left the .bib entry empty, I hadn't started using it yet. Still, a more helpful error message would have been nice!

(I haven't started using the plugin yet but this would be pretty much essential for me, so thanks in advance!)

Start by reproducing startup with the .bib entry left empty, then trace where the plugin attempts to open the unspecified path. The issue is done when this configuration produces a helpful, specific error instead of the generic ENOENT message.

Written by the indexing model from the issue text.