\balloonText applied to single note errors with symbol->string ??

[Thomas Morley]

Hi,

the code below

\layout { \context { \Voice \consists "Balloon_engraver" } }
{ c'-\balloonText #'(2 . 0) \markup { "1" } }

returns (in 2.21.0):
ERROR: In procedure symbol->string:
ERROR: Wrong type argument in position 1 (expecting symbol): ()

2.18.2 gives a more useful message:
/home/hermann/lilypond/usr/share/lilypond/current/scm/lily-library.scm:242:8:
In procedure symbol->string in expression (process-procedure book
paper ...):
/home/hermann/lilypond/usr/share/lilypond/current/scm/lily-library.scm:242:8:
Wrong type argument in position 1 (expecting symbol): ()

Though, I've no clue where symbol->string comes into the game...

Ofcourse the NR recommends to use balloonText _inside_ of chords, and
indeed the problem goes away, wrapping the note in an event-chord.
But shouldn't it work as a postevent to a single note, too??


Btw, it's present in all tested versions down to 2.12.3

Cheers,
  Harm