Prevent 500 error on search results if description contains relative link

Bug: If I add relative link to comment or description and search for it - I get 500 error on search page.

Reason for this is that we use `@repository` variable. But for pages like search it does not assigned.
In future we should avoid using such variables. Especially in markdown parser that can be used on different pages

Fixes #1601

See merge request !1111