If there are 0 results for listHITs, $scope.hits is not updated

[disperse]

Steps to reproduce:

1. Connect breadboard to an AMT account with hits in sandbox and 0 hits in production
2. Go to sandbox and view the list of HITs
3. Switch to production

Expected results: The list of sandbox HITs will be cleared.
Actual results: The list of sandbox HITs remains.

This is due to the code starting at line 201 in amt-admin.controler.js We need to handle 0 results on the first page properly.