avoid division by zero (units_per_EM is set to 0 for bitmap fonts)
avoid division by zero (units_per_EM is set to 0 for bitmap fonts)

lightmare/mapnik,naturalatlas/mapnik,naturalatlas/mapnik,naturalatlas/mapnik,tomhughes/mapnik,mapnik/mapnik,mapnik/mapnik,lightmare/mapnik,naturalatlas/mapnik,lightmare/mapnik,mapnik/mapnik,tomhughes/mapnik,lightmare/mapnik,mapnik/mapnik,tomhughes/mapnik,tomhughes/mapnik