Fix potential double-free in mbedtls_ssl_conf_psk()
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index d9b05fd..c1e29c7 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -5707,7 +5707,9 @@
         ( conf->psk_identity = mbedtls_calloc( 1, psk_identity_len ) ) == NULL )
     {
         mbedtls_free( conf->psk );
+        mbedtls_free( conf->psk_identity );
         conf->psk = NULL;
+        conf->psk_identity = NULL;
         return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
     }