MySQL syntax error unexpected '-'-Collection of common programming errors

I just noticed an error in my MySQL logs:

syntax error, unexpected ‘-‘, expecting FTS_TEXT or FTS_TERM or FTS_NUMB or ‘(‘

As far as I can tell this doesn’t relate to a query and doesn’t have a timestamp on it (all other entries in the log do). Has anyone seen this before? Does it relate to a configuration error or data corruption? Is it something malicious?