[igraph] error message -> crash.

[Figa Pelosa]

hallo,
I'm having this error:
python: vector.pmt:763: igraph_vector_resize: Assertion `v->stor_begin != 
((void *)0)' failed.
Aborted

..This is the code I'm using:

for step in range (1,numberOfSteps):
  try:
    vertexDisjointness=0
    for idx, v in enumerate(g.vs):
      print "idx:";idx
      for idx2, w in enumerate(g.vs):
        print"  idx2:";idx2
        ertexDisjointMedia += g.vertex_disjoint_paths(source=idx, target=idx2, 
checks=True, neighbors="ignore")
  except:
    vertexDisjointness=0

And this is my output:
idx:
0
  idx2:
1
python: vector.pmt:763: igraph_vector_resize: Assertion `v->stor_begin != 
((void *)0)' failed.
Aborted


What could it be? Is a problem with my graph or a bug?