Optical spacing fails at tight situations

[Janek Warchoł]

Hi,

didn't find it in the tracker so i report:
optical spacing doesn't work as expected in the following situation:

\version "2.13.43"
\new Score {
        \repeat unfold 12 { c''16 [ d'' b' c'' ] \noBreak }
}

All 16ths are spaced equally, while the distance betwwen d and b
should be smaller. When notes are not so tight, it works as expected,
try

\version "2.13.43"
\new Score {
        \repeat unfold 8 { c''16 [ d'' b' c'' ] \noBreak }
}

yours Pondly,
Janek