MeasureToolbar: Hides active sketch editor when no measure mode is selected

[jNery-zz]

MeasureToolbar: Hides active sketch editor when no measure mode is selected

Workaround:

• Ensure SketchEditor.IsVisible before starting a sketch

To reproduce:

• Add MeasureToolbar and assign to the same MapView
• Start Draw/Edit with default SketchEditor, no draw feedback is drawn

        xmlns:esri="http://schemas.esri.com/arcgis/runtime/2013">
    <Grid>
        <esri:MapView x:Name="MyMapView"/>
        <Button VerticalAlignment="Top" HorizontalAlignment="Right" Content="Draw" Click="OnDraw"/>
        <esri:MeasureToolbar x:Name="MyMeasureToolbar" MapView="{Binding ElementName=MyMapView}" VerticalAlignment="Top" HorizontalAlignment="Left"/>
    </Grid>

        public MainWindow()
        {
            InitializeComponent();

            MyMapView.Map = new Map(Basemap.CreateTopographic());
        }

        private async void OnDraw(object sender, RoutedEventArgs e)
        {
            try
            {
                // MyMapView.SketchEditor.IsVisible = true; // workaround
                var geometry = await MyMapView.SketchEditor.StartAsync(SketchCreationMode.Rectangle, false);
                var _ = MyMapView.SetViewpointAsync(new Viewpoint(geometry));
            }
            catch (TaskCanceledException)
            {

            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message, ex.GetType().Name);
            }
        }

Relevant code: https://github.com/Esri/arcgis-toolkit-dotnet/blob/master/src/Esri.ArcGISRuntime.Toolkit/Esri.ArcGISRuntime.Toolkit/UI/Controls/MeasureToolbar/MeasureToolbar.cs#L243
Add a check that one of the modes that need SketchEditor has been enabled before hiding current SketchEditor.

[williambohrmann3]

TODO: try to repro this with new GeometryEditor