pkcs15-lib: Fix cycling while selecting parent directory
pkcs15-lib: Fix cycling while selecting parent directory

Do not select parent when path length is 0

Thanks oss-fuzz
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=48056

LudovicRousseau/OpenSC,metsma/OpenSC,philipWendland/OpenSC,mouse07410/OpenSC,metsma/OpenSC,OpenSC/OpenSC,philipWendland/OpenSC,OpenSC/OpenSC,dengert/OpenSC,LudovicRousseau/OpenSC,mouse07410/OpenSC,mouse07410/OpenSC,dengert/OpenSC,LudovicRousseau/OpenSC,dengert/OpenSC,metsma/OpenSC,OpenSC/OpenSC,philipWendland/OpenSC