BUG/MINOR: events: fix nil dereference panic in Stop()

Stop() called h.listener.Close() without checking if listener is nil.
After Reset() sets listener to nil, or if the connection was never
established, calling Stop() would panic.

Author: mjuraga

client-native/events.go

@@ -116,7 +116,10 @@ func (h *HAProxyEventListener) Reset() {
 
 func (h *HAProxyEventListener) Stop() error {
 	h.stop.Store(true)
-	return h.listener.Close()
+	if h.listener != nil {
+		return h.listener.Close()
+	}
+	return nil
 }
 
 func newHAProxyEventListener(socketPath string) (*runtime.EventListener, error) {