Get 500 error instead of a 404

[matibarriento]

When you go to http://linkode.org/R you should get a 404 error because that linkode not (and can't) exist. Instead, you get a 500 error.

[facundobatista]

This is not solved yet by #118 (however behaviour improved).

After #118, it shows a generic "error getting linkode", while it should say something more appropiate, like "there is no linkode for that id"