BoringSSL: Fix PKCS12_parse() segfault when used without password

Unlike OpenSSL PKCS12_parse(), the BoringSSL version seems to require
the password pointer to be non-NULL even if no password is present. Map
passwrd == NULL to passwd = "" to avoid a NULL pointer dereference
within BoringSSL.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>

src/crypto/tls_openssl.c

@@ -2076,6 +2076,8 @@ static int tls_parse_pkcs12(SSL_CTX *ssl_ctx, SSL *ssl, PKCS12 *p12,
 	pkey = NULL;
 	cert = NULL;
 	certs = NULL;
+	if (!passwd)
+		passwd = "";
 	if (!PKCS12_parse(p12, passwd, &pkey, &cert, &certs)) {
 		tls_show_errors(MSG_DEBUG, __func__,
 				"Failed to parse PKCS12 file");