\repeat percent crashes on longer music expressions

[Jim Long]

The construct:

\version "2.16.1"

\score {
  \repeat percent 4 { R1*n }
}

crashes lilypond when n > 2:

GNU LilyPond 2.16.1
Processing `tiny.ly'
Parsing...
Interpreting 
music.../usr/local/share/lilypond/2.16.1/scm/music-functions.scm:318:21: In 
procedure car in expression (car durs):
/usr/local/share/lilypond/2.16.1/scm/music-functions.scm:318:21: Wrong type 
(expecting pair): ()

An improved error message would be helpful.

Pp. 141-142 of the 2.16.2 notation reference describe what the
user should expect when the music expression is two bars or less,
but do not indicate what is done with longer expressions.  This
section could be improved by stating the limits of \repeat
percent with respect to the length of the repeated music
expression.

A member of the user list commented that at some point, a
percent-repeated expression becomes too long, and a volta repeat
is in order.  Although I agree, I would be pleased if Lilypond
could be enhanced to successfully engrave percent repeats of four
bars or less in length.  I do not have a professionally engraved
example of such at this time.

Thank you!