MinGW Runtime Assertion error

[Karol Majewski]

Hi. The following code gives error. What am I doing wrong?

BEGIN==========================================================

\version "2.19.37"

PS =
#(ly:make-stencil
  (list 'embedded-ps
    "gsave
    currentpoint translate
    newpath
    0.125 setlinewidth
    0.0625 -0.5 moveto
    0.0625 0.5 lineto
    1.2375 0.5 lineto
    1.2375 -0.5 lineto
    closepath
    gsave
    fill
    grestore
    stroke
    grestore"
  )
  (cons 0 1.3125)
  (cons -0.5 0.5))

cluster =
#(lambda
  (grob)
  (let*
    ((sz
        (ly:grob-property grob 'font-size 0.0))
      (mult
        (magstep sz)))
    (set!
      (ly:grob-property grob 'stencil)
      (ly:stencil-scale PS mult mult))))

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  \tweak stencil \cluster g'8


END==========================================================