Return correct target for custom functors.
Return correct target for custom functors.

This fixes functor comparison which relies on the target() return value.

fmilano/mitk,MITK/MITK,fmilano/mitk,RabadanLab/MITKats,RabadanLab/MITKats,fmilano/mitk,danielknorr/MITK,rfloca/MITK,MITK/MITK,lsanzdiaz/MITK-BiiG,fmilano/mitk,NifTK/MITK,rfloca/MITK,MITK/MITK,lsanzdiaz/MITK-BiiG,NifTK/MITK,NifTK/MITK,RabadanLab/MITKats,NifTK/MITK,iwegner/MITK,lsanzdiaz/MITK-BiiG,danielknorr/MITK,rfloca/MITK,RabadanLab/MITKats,RabadanLab/MITKats,NifTK/MITK,MITK/MITK,lsanzdiaz/MITK-BiiG,fmilano/mitk,danielknorr/MITK,iwegner/MITK,danielknorr/MITK,iwegner/MITK,danielknorr/MITK,danielknorr/MITK,RabadanLab/MITKats,iwegner/MITK,danielknorr/MITK,rfloca/MITK,NifTK/MITK,iwegner/MITK,lsanzdiaz/MITK-BiiG,rfloca/MITK,fmilano/mitk,rfloca/MITK,lsanzdiaz/MITK-BiiG,MITK/MITK,lsanzdiaz/MITK-BiiG,rfloca/MITK,lsanzdiaz/MITK-BiiG,fmilano/mitk,iwegner/MITK,MITK/MITK