[C++][Fix bug] Properly parse urdf model having an empty base link
[C++][Fix bug] Properly parse urdf model having an empty base link

fvalenza/pinocchio,aelkhour/pinocchio,aelkhour/pinocchio,aelkhour/pinocchio,fvalenza/pinocchio,fvalenza/pinocchio,aelkhour/pinocchio,fvalenza/pinocchio