Missing title for indexed PDFs

[Marx1st]

Hi,

as mentioned in this issue: #1861 PDFs that don't contain a title won't get a clickable URL in the renderer.
I suggest inserting the URL as title when the document doesn't contain a title by itself (or create one from the content of the file). This can be pretty ugly, but users would be able to click the file in the renderer.

Regards
Tobias