[gmime] FIxed compile warning

[Jeffrey Stedfast <fejj src gnome org>]

commit 20faaf74b6f594f5a7c19fa3020801cb8fc38326
Author: Jeffrey Stedfast <jestedfa microsoft com>
Date:   Mon Dec 5 10:07:45 2016 -0500

    FIxed compile warning

 gmime/gmime-crypto-context.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gmime/gmime-crypto-context.c b/gmime/gmime-crypto-context.c
index e610b7d..ef160cc 100644
--- a/gmime/gmime-crypto-context.c
+++ b/gmime/gmime-crypto-context.c
@@ -866,7 +866,7 @@ g_mime_decrypt_result_set_session_key (GMimeDecryptResult *result, const char *s
 const char *
 g_mime_decryption_result_get_session_key (GMimeDecryptResult *result)
 {
-       g_return_val_if_fail (GMIME_IS_DECRYPT_RESULT (result), GMIME_DIGEST_ALGO_DEFAULT);
+       g_return_val_if_fail (GMIME_IS_DECRYPT_RESULT (result), NULL);
        
        return result->session_key;
 }