adjust the synchronization in check syntax for reading doc results to cope with the case where the thread has been killed (the nacks are apparently not triggered on thread death in some cases)
adjust the synchronization in check syntax for reading doc results to
cope with the case where the thread has been killed (the nacks are
apparently not triggered on thread death in some cases)

(optimistically) closes PR 12427

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