Comment 3 for bug 943282

Found a fix : the bug is produced by GooCanvas function like this :
" g_object_get(item,"center_x",&cx,"center_y",&cy,"radius_x",&rx,"radius_y",&ry,NULL); "

We get NEGATIVE values for ry ! (i.e. the ellipse's radius for y coordinates)

So I've added some code to get only POSITIVE radius.