Segmentation fault when trying to create custom graph

[meme mondo]

Hi! I'm trying to create a custom graph like reported in the code from a text file. When I run the code I have had the segmentation fault error, so I used the gbd and it presented me the following statement:
Starting program: /home/tesi/OGDF-snapshot/build-make/conn1

Program received signal SIGSEGV, Segmentation fault.
0x00000000004220db in ogdf::Graph::newEdge(ogdf::NodeElement*, ogdf::NodeElement*) ()

I don't undestand where is the error.
Please help me!
Thanks!