#4 map_Ka material attribute crashes GLC for OBJ import

[Eric Haines]

The OBJ "MTL" format allows map_Ka.

newmtl Stone
Ns 0
Ka 0.2 0.2 0.2
Kd 1 1 1
Ks 0 0 0

map_Ka beds-RGB.png

map_Kd beds-RGB.png
illum 2

This is for a textured material. If you use this material with the map_Ka line uncommented, GLC dies. map_Ka is a valid argument, see http://en.wikipedia.org/wiki/Wavefront_.obj_file#Texture_maps.