#2 ReactiveNavigationDemo crashes with VFF method

[J.L. Blanco]

Thanks to Xuan Vu for reporting:

with the ReactiveNavigationDemo when I change HOLONOMIC_METHOD=0 (choose VFF method) it has no results, there are warning such as:

stlplus::null_dereference: null pointer dereferenced in smart_ptr::operator->[CReactiveNavigationSystem::performNavigationStep] Exceptions!!