Saving report with dashlet enabled for non admin users can cause a backtrace

When saving a report with dashboard enabled, CiviCRM saves a record in both civicrm_dashboard and civicrm_dashboard_contact.

If you are an admin, it saves a record in civicrm_dashboard_contact for every contact already in that table that doesn't already have a record for this dashboard item.

If you are not an admin, it saves the record in civicrm_dashboad_contact just for you, but it doesn't check if you already have a record for this contact_id/dashboard_id combo, thus resulting in a db constraint violation if you already have the record.