fix argument to isnan() in simu.cpp
fix argument to isnan() in simu.cpp

casting car->ctrl-gear to float to avoid compile errors
ugo-nama-kun/gym_torcs,travistang/late_fyt,travistang/late_fyt,ugo-nama-kun/gym_torcs,ugo-nama-kun/gym_torcs,ugo-nama-kun/gym_torcs,ugo-nama-kun/gym_torcs,travistang/late_fyt,travistang/late_fyt,ugo-nama-kun/gym_torcs,ugo-nama-kun/gym_torcs,travistang/late_fyt,travistang/late_fyt,travistang/late_fyt