fix a compiler warning in raster
fix a compiler warning in raster

RobertoMalatesta/glshim,lunixbochs/glshim,RobertoMalatesta/glshim,lunixbochs/glshim,seandepagnier/glshim,RobertoMalatesta/glshim,seandepagnier/glshim,lunixbochs/glshim,seandepagnier/glshim,lunixbochs/glshim,seandepagnier/glshim,RobertoMalatesta/glshim