Check empty stream endpoints for 404 compatibility

[dsheets]

#113 points out that some stream endpoints can be empty and, when they are, the API returns 404. We should check the various stream endpoints for this behavior (or find reference in GitHub's docs about it) and then handle it appropriately.

[dsheets]

This should really apply to all endpoints that can result in 404 because the object is missing or inaccessible. The functions which bind these endpoints should return an option or an 'a result.