1062 Duplicate entry @ tracker_agents_name_hash_unique

**Describe the bug**
`SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '477c02627521747f77ac6150d7a63f1f4946bd41197ec2143e4eaccd6407271e' for key 'tracker_agents_name_hash_unique' (SQL: insert into `tracker_agents` (`name`, `browser`, `browser_version`, `name_hash`, `updated_at`, `created_at`) values (Mozilla/5.0 (Linux; Android 8.1.0; SM-G610F Build/M1AJQ; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/70.0.3538.110 Mobile Safari/537.36, Chrome Mobile WebView, 70.0.3538, 477c02627521747f77ac6150d7a63f1f4946bd41197ec2143e4eaccd6407271e, 2019-11-06 19:03:51, 2019-11-06 19:03:51)) {"exception":"[object] (Illuminate\\Database\\QueryException(code: 23000): SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '477c02627521747f77ac6150d7a63f1f4946bd41197ec2143e4eaccd6407271e' for key 'tracker_agents_name_hash_unique' (SQL: insert into `tracker_agents` (`name`, `browser`, `browser_version`, `name_hash`, `updated_at`, `created_at`) values (Mozilla/5.0 (Linux; Android 8.1.0; SM-G610F Build/M1AJQ; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/70.0.3538.110 Mobile Safari/537.36, Chrome Mobile WebView, 70.0.3538, 477c02627521747f77ac6150d7a63f1f4946bd41197ec2143e4eaccd6407271e, 2019-11-06 19:03:51, 2019-11-06 19:03:51))`

Start by tracing the code path that inserts into the tracker_agents table and inspect the tracker_agents_name_hash_unique constraint. Reproduce the duplicate-entry case and determine the expected behavior when the same name_hash is encountered. Done means the reported SQLSTATE 23000 failure no longer occurs while the uniqueness rule remains respected.

Written by the indexing model from the issue text.