Avoid division by zero in case width or height for page are not specified

traceback:
File "/home/developer/WorkData/PLC/beremiz/beremiz/editors/Viewer.py", line 3755, in OnPaint
self.DoDrawing(dc)
File "/home/developer/WorkData/PLC/beremiz/beremiz/editors/Viewer.py", line 3723, in DoDrawing
for y in xrange(self.PageSize[1] - (ystart * SCROLLBAR_UNIT) % self.PageSize[1], int(window_size[1] / self.ViewScale[1]), self.PageSize[1]):
<type 'exceptions.ZeroDivisionError'>: integer division or modulo by zero

#!/bin/sh

INKSCAPE=inkscape

for fname in `ls *.svg`; do
    for i in `cat $fname |grep -o -e '%%[^%]*%%'|sed 's/%//g'` 
    do
        if [ $i.png -nt $fname ]; then
 	    echo "Skip $i"
        else
	    rm  -f $i.png
	    echo "$INKSCAPE" $fname -z -e $i.png -i $i
	    "$INKSCAPE" $fname -z -e $i.png -i $i
        fi
    done
done

cp ico024.png brz.png
convert -compress none ico*.png brz.ico
rm -f ico*.png


convert -compress none poeico*.png poe.ico
rm -f poeico*.png