Saving a shortlink edit redirects to 404

[jameslzhu]

Reported by jaymo.

On saving a shortlink edit, for instance, from a url like this:

https://hkn.eecs.berkeley.edu/shortlinks/243/edit

The page is redirected to the (ostensibly) shortlink detail view page:

https://hkn.eecs.berkeley.edu/shortlinks/243/

However, this page does not exist, so a 404 error is returned.

Instead, this page should redirect to the main shortlinks page (potentially with an announcement banner confirming success):

https://hkn.eecs.berkeley.edu/shortlinks/

[alexander-zw]

Is someone gonna fix this lol