old-straight-flag + smaller Stem.thickness gives no output and huge overflow

[Karol Majewski]

The following code gives:
warning: cannot fit music on page: overflow is 1096.382978
and no output. Perhaps it's a bug?

\version "2.17.19"

\layout {
  \context {
    \Score
    \override Stem.thickness = #1.2
    \override Flag.stencil = #old-straight-flag
}
}

{
c'16 r r d' c' r r d' c' r r d' c' r r d'
c' r r d' c' r r d' c' r r d' c' r r d'
c' r r d' c' r r d' c' r r d' c' r r d'
}

When I set Stem.thickness to default (1.3) everything is OK.

Version 2.16.2 gives valid output regardless of Stem.thickness value.