An uninitialized MARKUP EVENT instance has been passed to the markup processor.

#6142   Run-time catchable error

An uninitialized MARKUP EVENT instance has been passed to the markup processor.

Explanation

The markup source value given to do markup-parse can consist of strings and signalled markup events. The signalled markup-event values must be obtained from #content or #current-markup-event. This error indicates that a markup-event value from a different source has been signalled as input to do markup-parse.