Stepper fix for possible race condition
Stepper fix for possible race condition

Uses queue-callback to avoid a possible race condition in updating of editor
on non-eventspace thread.

Fixes PR 12217

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket