Problem: missing rc checks in udp_engine

Solution: add them

src/udp_engine.cpp

@@ -396,8 +396,8 @@ void zmq::udp_engine_t::out_event ()
     if (rc == 0) {
         msg_t body_msg;
         rc = _session->pull_msg (&body_msg);
-        //  TODO rc is not checked here. We seem to assume rc == 0. An
-        //  assertion should be added.
+        //  If there's a group, there should also be a body
+        errno_assert (rc == 0);
 
         const size_t group_size = group_msg.size ();
         const size_t body_size = body_msg.size ();
@@ -412,7 +412,7 @@ void zmq::udp_engine_t::out_event ()
                 rc = group_msg.close ();
                 errno_assert (rc == 0);
 
-                body_msg.close ();
+                rc = body_msg.close ();
                 errno_assert (rc == 0);
 
                 return;