[gmime] Protect against dereferencing a NULL subkey

[Jeffrey Stedfast <fejj src gnome org>]

commit b6bc2f8864778747762f56e08a3247109a39ebd5
Author: Jeffrey Stedfast <jestedfa microsoft com>
Date:   Tue Mar 14 19:57:12 2017 -0400

    Protect against dereferencing a NULL subkey

 gmime/gmime-gpgme-utils.c |   23 +++++++++++------------
 1 files changed, 11 insertions(+), 12 deletions(-)
---
diff --git a/gmime/gmime-gpgme-utils.c b/gmime/gmime-gpgme-utils.c
index a9cf380..61bbe73 100644
--- a/gmime/gmime-gpgme-utils.c
+++ b/gmime/gmime-gpgme-utils.c
@@ -97,8 +97,7 @@ g_mime_gpgme_passphrase_callback (void *hook, const char *uid_hint, const char *
 }
 
 
-#define KEY_IS_OK(k)   (!((k)->expired || (k)->revoked ||      \
-                          (k)->disabled || (k)->invalid))
+#define KEY_IS_OK(k)   (!((k)->expired || (k)->revoked || (k)->disabled || (k)->invalid))
 
 static gpgme_key_t
 g_mime_gpgme_get_key_by_name (gpgme_ctx_t ctx, const char *name, gboolean secret, GError **err)
@@ -123,18 +122,18 @@ g_mime_gpgme_get_key_by_name (gpgme_ctx_t ctx, const char *name, gboolean secret
                if (KEY_IS_OK (key)) {
                        subkey = key->subkeys;
                        
-                       while (subkey && ((secret && !subkey->can_sign) ||
-                                         (!secret && !subkey->can_encrypt)))
+                       while (subkey && ((secret && !subkey->can_sign) || (!secret && !subkey->can_encrypt)))
                                subkey = subkey->next;
                        
-                       if (subkey && KEY_IS_OK (subkey) && 
-                           (subkey->expires == 0 || subkey->expires > now))
-                               break;
-                       
-                       if (subkey->expired)
-                               errval = GPG_ERR_KEY_EXPIRED;
-                       else
-                               errval = GPG_ERR_BAD_KEY;
+                       if (subkey) {
+                               if (KEY_IS_OK (subkey) && (subkey->expires == 0 || subkey->expires > now))
+                                       break;
+                               
+                               if (subkey->expired)
+                                       errval = GPG_ERR_KEY_EXPIRED;
+                               else
+                                       errval = GPG_ERR_BAD_KEY;
+                       }
                } else {
                        if (key->expired)
                                errval = GPG_ERR_KEY_EXPIRED;