agent: Fix possible memory leak.

src/agent.c

@@ -287,9 +287,14 @@ int ssh_agent_get_ident_count(struct ssh_session_struct *session) {
 
   /* send message to the agent requesting the list of identities */
   request = ssh_buffer_new();
+  if (request == NULL) {
+      ssh_set_error_oom(request);
+      return -1;
+  }
   if (buffer_add_u8(request, c1) < 0) {
-    ssh_set_error(session, SSH_FATAL, "Not enough space");
+      ssh_set_error_oom(request);
-    return -1;
+      ssh_buffer_free(request);
+      return -1;
   }
 
   reply = ssh_buffer_new();