Broken melisma

[Nicolas Sceaux]

Hi,

%{
In case of multiple vocal staves, __ extender lines in melisma may be  
broken,
as is shown in the following example:
%}
\version "2.13.1"

staffA=\new Staff <<
  \new Voice = "A" \with { autoBeaming = ##f } {
    g'4. \melisma g'8 g'2 g' \melismaEnd g'
  }
  \lyricsto "A" \new Lyrics \lyricmode { bla __ bla }
>>

staffB=\new Staff <<
  \new Voice = "B" \with { autoBeaming = ##f } {
    c'4 c' c' c' c' c' c' c'
  }
  \lyricsto "B" \new Lyrics \lyricmode {
    bla blu bli blo bla blu bli blo
  }
>>

%% Melisma as expected
{ \staffA }

%% Broken melisma
<< \staffA \staffB >>