[poppler] Bug with drawImageMaskPrescaled

[Salvatore De Paolis]

Hi all
while working on PopplerLinkMapping for the pdf viewer plugin(claws mail) I
discover i got a SIGFPE while rotating a document.
It happends cause in drawImageMaskPrescaled there's no check for scaleHeight ==
0. Adding a check and set to 1 the value doesn't help (as it's done for
scaleWidth) cause it show a blank document.

While rotating on certain conditions (not in all cases) it happends to have

 /* this scaling code is adopted from the splash image scaling code */
  cairo_get_matrix(cairo, &matrix);

matrix which is firstly 0 and after nan so seems to be the problem in
cairo_get_matrix which fail to fill the CTM.

What's actually the difference btw drawImageMaskPrescaled and
drawImageMaskRegular?

I substitute the first method (which do not uses cairo_get_matrix) with this
last one and it fixes the problem.

Regards
S.