email: fix fallback sending to multiple admins If no recipients are set, emails are sent to all admins and the address specified in the config file setting 'email_to'. However, the existing code did not cater for the fact that multiple addresses could be set there: the setting was treated as a single string and passed along as-is. Adapt the code to split the email_to contents on a comma, as this is the separator expected by backlash.