Multi_measure_rest::get_rods (): I am not spanned!

[Dan Eble]

*** Unexpected Output ***
programming error: Object is not a markup.
This object should be a markup: ()
programming error: Multi_measure_rest::get_rods (): I am not spanned!

These are the same messages as in 
https://code.google.com/p/lilypond/issues/detail?id=1291 (Oct 4, 2010).  I 
don’t know whether this is a new problem or just a new way to reproduce that 
same old problem.

*** Input ***
\version "2.19.15"

chordNames = \chordmode {
  f1 | %{nothing in final measure%}
}

leadNotes = \relative {
  f'1 | R1
}

words = \lyricmode {
  Blah
}

<<
  \new ChordNames {
    \chordNames
  }

  \new ChoirStaff
  <<
    \new Staff <<
      \new Voice = "lead" { \leadNotes }
    >>

    \new Lyrics <<
      \lyricsto lead { \words }
    >>
  >>
>>

*** Commit ***
For my input, these messages appeared after this commit:

commit b12ee555e33d483eed0832d8502ad7a282ef9796
Author: David Kastrup <address@hidden>
Date:   Mon Oct 6 00:31:58 2014 +0200

    Issue 2010: \lyricsto may turn into a voice-mangling zombie
    
    The problem here was that the simultaneous iterator might keep
    rerhythmed lyrics around when the associated voice has died already,
    blocking the simultaneous iterator.  The solution is that when removing
    the last regular iterator to remove all remaining lyric-combined
    iterators at the same time.

Regards,
— 
Dan