Fix error in RigidRegistration example
Fix error in RigidRegistration example

https://github.com/SuperElastix/SimpleElastix/issues/111
kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix,kaspermarstal/SimpleElastix