added checks in test-registrable-domain.c
added checks in test-registrable-domain.c

dago/libpsl,darnir/libpsl,dkg/libpsl,rockdaboot/libpsl,dago/libpsl,dkg/libpsl,rockdaboot/libpsl,rockdaboot/libpsl,dago/libpsl,darnir/libpsl,darnir/libpsl