make sure gf_file_exists return false for directory
make sure gf_file_exists return false for directory

rbouqueau/gpac,gpac/gpac,gpac/gpac,rbouqueau/gpac,gpac/gpac,gpac/gpac,rbouqueau/gpac,gpac/gpac,gpac/gpac,rbouqueau/gpac,gpac/gpac,rbouqueau/gpac,rbouqueau/gpac,rbouqueau/gpac,rbouqueau/gpac,gpac/gpac