Division by zero

[CryptoPirat3]

Describe the bug
Program doesn't check if parameter ysize equal to zero. It leads to Arithmetic exception

To Reproduce
Steps to reproduce the behavior:

1. First of all build from sources cups-filters-2.0.1, libcupsfilters-2.1.1, libppd-2.1.1, pdfio-1.6.1
2. Run imagetoraster with Crash seed (finding 279).txt file

Expected behavior
Normal completion of excecutable

Source

    135        z->xmod    = z->width % z->xsize;
    136        z->xstep   = z->width / z->xsize;
    137        z->xincr   = 1;
    138        z->ymod    = z->height % z->ysize;
--->139        z->ystep   = z->height / z->ysize;
    140        z->yincr   = 1;
    141        z->instep  = z->xstep * z->depth;
    142        z->inincr  = /* z->xincr * */ z->depth; // z->xincr is always 1
    143    
    144        if (z->width < img->ysize)

Executable log

#0  0x0000555555686fad in _cfImageZoomNew (img=0x55555598d7c0, xc0=0, yc0=0, xc1=xc1@entry=767, yc1=<optimized out>, xsize=2093, ysize=0, rotated=1, type=CF_IZOOM_NORMAL) at /src/libcupsfilters-2.1.1/cupsfilters/image-zoom.c:139
#1  0x00005555555f99e7 in cfFilterImageToRaster (inputfd=inputfd@entry=3, outputfd=<optimized out>, outputfd@entry=1, inputseekable=inputseekable@entry=1, data=data@entry=0x7fffffffc668, parameters=parameters@entry=0x0) at /src/libcupsfilters-2.1.1/cupsfilters/imagetoraster.c:1678
#2  0x0000555555566202 in ppdFilterCUPSWrapper (argc=argc@entry=7, argv=argv@entry=0x7fffffffc978, filter=0x5555555f3f10 <cfFilterImageToRaster>, parameters=parameters@entry=0x0, JobCanceled=0x55555570ac90 <JobCanceled>) at /src/libppd-2.1.1/ppd/ppd-filter.c:179
#3  0x0000555555565cd4 in main (argc=7, argv=0x7fffffffc978) at /src/cups-filters/filter/imagetoraster.c:73