Missing text format: .


I’m having this strange alert that is filling up my D7 dblog madly:

Type filter
Message Missing text format: .
Severity alert

As you can see, the missing format looks just EMPTY, only the dot is mentioned, and therefor I could not find any fix on drupal.org or elsewhere.

Any hint about how to fix it is most welcome.

Drupal version: 

Source: https://www.drupal.org/taxonomy/term/22/feed