REFL045 should not warn when unknown flags.

[JohanLarsson]

        private void OnSourcePropertyChanged(object sender, PropertyChangedEventArgs e)
        {
            if (string.IsNullOrEmpty(e.PropertyName))
            {
                this.OnResetProperties(sender, e);
                return;
            }

            var propertyInfo = sender.GetType().GetProperty(e.PropertyName, this.Settings.BindingFlags);