Fix exception handling when trying to parse an edit as anonymous user

Accessing a file in a change edit (http://host:8080/#/c/3/edit/test.txt)
as not signed in user failed with Internal Server Error, rather than
saying that the user must sign in.

Change-Id: I7f19e13e3f5663598daa0a4f63ca24a3f7eb844e
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
2 files changed