wgengine/monitor: don't return nil, nil in darwin monitor
We used to allow that, but now it just crashes.
Separately I need to figure out why it got into this path at all,
which is
@@ -58,7 +58,7 @@ func (m *darwinRouteMon) Receive() (message, error) {
msgs, err := route.ParseRIB(route.RIBTypeRoute, m.buf[:n])
if err != nil {
m.logf("read %d bytes (% 02x), failed to parse RIB: %v", n, m.buf[:n], err)
- return nil, nil
+ return unspecifiedMessage{}, nil
}
if debugRouteMessages {
m.logf("read: %d bytes, %d msgs", n, len(msgs))
