Spacing/collision behaviour of NullVoice

[Urs Liska]

Having a look at the Changes page referenced by Federico I wanted to 
experiment with the example for the new NullVoice.

I thought it might be useful to add a different kind of example with a 
different rhythm for visible notes and lyrics.

However I noticed a behaviour I wouldn't have expected:

Try out the following snippet:

soprano = \relative c' { c e g c }
verse = \lyricmode { This is my song }

\score {
  \new Staff <<
     %\soprano
     { \oneVoice r4. r4 r4. }
    \new NullVoice = "aligner" \soprano
    \new Lyrics \lyricsto "aligner" \verse
  >>
  \layout {}
}

The rests are placed wrongly, obviously avoiding _something_.

If you comment out the NullVoice the rests are placed correctly.
If you uncomment the \soprano they are also placed correctly (but 
differently).

Is this intended behaviour?

Urs