libcacard/vcard_emul_nss: don't stop thread when there are no slots

    SECMODModule *module = (SECMODModule *)arg;

    do {

        /*

         * XXX - the latency value doesn't matter one bit. you only get no

         * blocking (flags |= CKF_DONT_BLOCK) or PKCS11_WAIT_LATENCY (==500),

         * hard coded in coolkey.  And it isn't coolkey's fault - the timeout

         * value we pass get's dropped on the floor before C_WaitForSlotEvent

         * is called.

         */

        slot = SECMOD_WaitForAnyTokenEvent(module, 0, 500);

        if (slot == NULL) {

            /* this could be just a no event indication */

            if (PORT_GetError() == SEC_ERROR_NO_EVENT) {

                continue;

            }

            break;

        }

        vreader = vcard_emul_find_vreader_from_slot(slot);