Issue 2118 in lilypond: Overriding stencil of StringNumber leads to "programming error"messages

[lilypond]

Status: Accepted
Owner: ----
Labels: Type-Defect

New issue 2118 by address@hidden: Overriding stencil of StringNumber  
leads to "programming error"messages
http://code.google.com/p/lilypond/issues/detail?id=2118

David Kastrup reports:

the awful spacing of input/regression/tablature-harmonic-functions.ly
let me to investigate, and it is apparently due to StringNumber being
set to transparent, meaning that it still occupies space.  I tried now
to do

\new Voice \with { \override StringNumber #'stencil = ##f }
{ \clef "treble_8"
 e,1 | % check whether tab note head is restored
 \harmonicByFret #12 e'4\1 ~
 \harmonicByFret #12 e'4\1 (
 \ottava #1
 \harmonicByFret #7 e'4\1)
 \harmonicByFret #5 e'8\1
 \ottava #2
 \harmonicByFret #4 < b\2 e'\1 >8 |
 \harmonicByFret #3 < g\3 b\2 e'\1 >4
 \harmonicByFret #2.7 < g\3 b\2 e'\1 >4
 \harmonicByFret #2.3 < g\3 b\2 e'\1 >4
 \harmonicByFret #2 < g\3 b\2 e'\1 >4 |
 \ottava #0
}

instead (removing the New_fingering_engraver is not an option since it
is responsible for more than just string numbers), but I get programming
errors in return:

Interpreting music...
Preprocessing graphical objects...
programming error: cannot align on self: empty element
continuing, cross fingers