messages: Fix NULL check, preventing SEGFAULT

The wrong conditional check for newly allocated memory would make the
function to fail when the allocation was successful and access invalid
memory when the allocation failed.

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>

src/messages.c

@@ -448,7 +448,7 @@ static void ssh_message_queue(ssh_session session, ssh_message message)
 
     if (session->ssh_message_list == NULL) {
         session->ssh_message_list = ssh_list_new();
-        if (session->ssh_message_list != NULL) {
+        if (session->ssh_message_list == NULL) {
             /*
              * If the message list couldn't be allocated, the message can't be
              * enqueued