subgraph_isomorphism on filtered graph / GraphView => segfaults

I have fixed this now in the git version, please check it out.
Thanks for noticing this and providing a simple example!

Hi Tiago,

Thank you very much for your super-fast fix! I checked the git version,
and I do not get any segfaults anymore. Back to finding bugs in my code
for now :slight_smile:

Best,
Ingo