[kernel] fix compilation error in debug mode
[kernel] fix compilation error in debug mode

siconos/siconos,radarsat1/siconos,bremond/siconos,radarsat1/siconos,bremond/siconos,radarsat1/siconos,bremond/siconos,fperignon/siconos,radarsat1/siconos,bremond/siconos,siconos/siconos,fperignon/siconos,siconos/siconos,fperignon/siconos,fperignon/siconos,fperignon/siconos,radarsat1/siconos,siconos/siconos,bremond/siconos