"Attempted to dereference zero pointer", error

[Arij Souai]

Hi

Im working on adding routing in my simulation :

 
  Ipv4GlobalRoutingHelper::PopulateRoutingTables ();

But when i add it it show this error :

assert failed. cond="m_ptr", msg="Attempted to dereference zero pointer", file=./ns3/ptr.h, line=630
terminate called without an active exception
Command ['/home/tpc/ns-allinone-3.31/ns-3.31/build/scratch/x2'] terminated with signal SIGIOT. Run it under a debugger to get more information (./waf --run <program> --gdb").

Can anyone please tell me the reason why this error appears?

Thank you