Use fallback if favicon cannot be resolved in snippet preview

[Sebobo]

Currently the snippet preview tries to render the favicon.ico in the web folder and will render an error in the browser console if none is found. Also the is a white space instead of the favicon in the search preview.

But the favicon might not exist or another favicon is linked in the page metadata.
Therefore the linked one should be used or a fallback if no favicon is found at all.

[Sebobo]

Fixed in 1.1.1