Midi lyrics barcheck warnings

[Erik Sandberg]

Hi,

Incorrect midi barcheck warnings are happening again. This time I was unable 
to isolate what causes it; random & unrelated changes seem to affect it. I 
couldn't get it much smaller than this:

%Lilypond produces correct output, but during midi output, it produces a 
%barcheck warning for the last barcheck in the lyrics.
%The problem disappears e.g. if you remove the first staff, or if you remove 
%the first 3 bars, or if you change the tie in bar 27 to a slur.

\version "2.2.0"

\score {
<<
\new Staff \notes {
\time 6/8
r2. r r 
r r r
r r r r r r r r
r r r r r r 
r r r r r r
b8 b b b b b 
} 

\new Staff \context Voice=A \notes {
  \time 6/8
  R2. | R2. | R2. | 
  % 4
  r4 r8 r4 a8  |
  % 5
  a4  d'8  d'4  cis'8  |
  % 6
  b4  b8 r8 r8  b8  |
  % 7
  a4.~ a4 g8  |
  % 8
  a4.  fis8  r8  a8  |
  % 9
  a4  d'8  d'4  cis'8  |
  % 10
  b4.  cis'4.  |
  % 11
  a4  d'8   cis'4.  |
  % 12
  a4  r8 r4 r8 | R2. |
  % 14
  r4 r8 r4 a8  |
  % 15
  a4  a8   a4 fis8  |
  % 16
  g4.  c'4.  |
  % 17
  a4  a8   d'4.  |
  % 18
  b4  r8 r4  g8  |
  % 19
  d'4  a8   b4 g8  |
  % 20
  d'4.  ais4.  |
  % 21
   b4 d'8  d4. |
  % 22
  d4  r8 r4 r8 | R2. | 
  % 24
  r4 r8 r4 a8  |
  % 25
  a4 d8 d4 cis8 |
  % 26
  cis'4.  b4.  |
  % 27
  a4~ a4 g4  |
  % 28
  a4.  fis4  r8  |
} 

\lyricsto A \new Lyrics \lyrics {
  a4 | a a a a | a a a | a a | a a
  a a a a a | a a | a a a | a
  a | a a a a | a a | a a a | a
  a | a a a a | a a | a a a | a
  a | a a a a | a a | a b | c d
}
>>
\midi {\tempo 4=100 }
\paper{}
}