How to remove the “Folder” icon in the DropDownMenu of the HierarchyNavigator?

<Style  TargetType="{x:Type syncfusion:HierarchyNavigatorDropDownItem}">
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="{x:Type syncfusion:HierarchyNavigatorDropDownItem}">
                            <Grid x:Name="PART_Root" Background="Transparent"  Opacity="{TemplateBinding Opacity}" MinHeight="26">
                                <VisualStateManager.VisualStateGroups>
                                    <VisualStateGroup x:Name="CommonStates">
                                        <VisualState x:Name="Normal"/>
                                        <VisualState x:Name="MouseOver">
                                            <Storyboard>
                                                <DoubleAnimation Duration="0" Storyboard.TargetName="PART_MouseOverRoot" Storyboard.TargetProperty="Opacity" To="1"/>
                                            </Storyboard>
                                        </VisualState>
                                    </VisualStateGroup>
                                </VisualStateManager.VisualStateGroups>
                                <Border x:Name="PART_MouseOverRoot" Opacity="0" BorderThickness="1" Background="{StaticResource HierarchyNavigatorMenuItemMouseOverBrushKey}" BorderBrush="{StaticResource HierarchyNavigatorMenuItemMouseOverBorderBrush}" CornerRadius="2" />
                                <Border x:Name="PART_BorderRoot" BorderThickness="1" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" CornerRadius="2">
                                    <Grid x:Name="PART_LayoutRoot">
                                        <Grid.ColumnDefinitions>
                                            <ColumnDefinition Width="30" />
                                            <ColumnDefinition />
                                        </Grid.ColumnDefinitions>
                                        <Canvas x:Name="PART_FolderIcon" Visibility="Collapsed" Margin="0,1" Width="14" Height="16" Canvas.Left="0" Canvas.Top="0">
                                        </Canvas>
                                        <ContentControl x:Name="PART_ContentControl" HorizontalAlignment="Left" VerticalAlignment="Center" Content="{TemplateBinding Content}" 
                                                FontWeight="{TemplateBinding HighLightSelectedItem}" ContentTemplate="{TemplateBinding ContentTemplate}" Margin="3,0,2,0" Grid.Column="1" 
                                                Foreground="{TemplateBinding Foreground}" FontFamily="{TemplateBinding FontFamily}" FontSize="{TemplateBinding FontSize}" />
                                    </Grid>
                                </Border>
                            </Grid>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>

<syncfusion:HierarchyNavigator  x:Name="hierarchyNavigator1" 
 ItemsSource="{Binding FileItems}" ItemTemplate="{StaticResource ItemGroupTemplate}" >
 </syncfusion:HierarchyNavigator>