Allowed hosts not configured warning

Sonarr version (exact version): 4.0.20.3014
Mono version (if Sonarr is not running on Windows):
OS: QNAP NAS
Debug logs:
Description of issue:
Sonarr is warning that ‘Allowed Hosts is not configured, Sonarr will accept requests for any hostname or IP address’ but this is a valid setting (and actually what I want) so how do I stop this warning from appearing?