Initialize hash_len before using it

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 4a1191a..d868e49 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -2874,7 +2874,7 @@
 int mbedtls_ssl_parse_finished( mbedtls_ssl_context *ssl )
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
-    unsigned int hash_len;
+    unsigned int hash_len = 12;
     unsigned char buf[SSL_MAX_HASH_LEN];
 
     MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse finished" ) );
@@ -2896,8 +2896,6 @@
         goto exit;
     }
 
-    hash_len = 12;
-
     if( ssl->in_msg[0] != MBEDTLS_SSL_HS_FINISHED  )
     {
         mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,