[graph-tool] Read graph empty?

Hi, can you tell me what I am doing wrong in the attached code? The graph I used can be found here: www.tessarakt.de/stuff/planar100k.graphml.zip (1,5 MB ...) When I run it, it says $ ./1 #vertices: 0 make_map_as_colormap entered writing something to MapAsColorMap Speicherzugriffsfehle The crash is due to the empty graph ... It should be possible to add vertices to adjacency_list<vecS, vecS, bidirectionalS, VertexProperties, EdgeProperties>?!?! Cheers, Jens