Fix use of uninitialised ret ssl_tls.c

library/ssl_tls.c

@@ -221,7 +221,7 @@ static int ssl3_prf( const unsigned char *secret, size_t slen,
                      const unsigned char *random, size_t rlen,
                      unsigned char *dstbuf, size_t dlen )
 {
-    int ret;
+    int ret = 0;
     size_t i;
     mbedtls_md5_context md5;
     mbedtls_sha1_context sha1;