These redirects are already in place for the courseware, and will
redirect to the outline page, or the dashboard, or wherever, based
on the type of access error (unenrolled, access expired, survey
needed, etc).
This commit stops the course home tabs from paying attention to the
401 error messages coming from the backend - course_access in the
metadata API handles that now.
This commit also changes our useModel hook to more gracefully handle
not being able to find the model - it is a valid case we want to
allow (still will cause problems if you actually try to use the data,
but will at least provide an object you can inspect).
b4bedfe3f0