How do I troubleshoot the error
Theme key "" not found?
I found dozens of search results regarding specific keys, but nothing useful for debugging an empty key ("").
Here is the full entry from syslog:
Sep 12 09:45:47 core drupal: http://www.example.com|1347457547|theme|192.168.1.10|http://www.example.com/|http://www.example.com/admin/config/development/logging|1||Theme key "" not found.
What exactly triggers this error and how should I go about debugging it?