TreeView Templates throw null exception Declined - Not Valid

I cannot seem to get the TreeView templates working without throwing a NullReferenceException. No matter how I try setting up the templates, it always throws the following exception: 

blazor.server.js:15 [2019-10-06T15:36:30.998Z] Error: System.NullReferenceException: Object reference not set to an instance of an object. at System.Object.GetType() at Syncfusion.EJ2.Blazor.Navigations.TreeViewTemplates.BuildRenderTree(RenderTreeBuilder __builder) at Microsoft.AspNetCore.Components.ComponentBase.<.ctor>b__6_0(RenderTreeBuilder builder) at Microsoft.AspNetCore.Components.Rendering.ComponentState.RenderIntoBatch(RenderBatchBuilder batchBuilder, RenderFragment renderFragment) at Microsoft.AspNetCore.Components.RenderTree.Renderer.RenderInExistingBatch(RenderQueueEntry renderQueueEntry) at Microsoft.AspNetCore.Components.RenderTree.Renderer.ProcessRenderQueue() 

Below is a code example I've simplified as much as possible to show the problematic templates. The first EjsTreeView renders and works correctly, but the second throws the above exception. 

@page "/treeviewtmpl"
@using Phoenix.Web.ViewModels;
@using Phoenix.Nav.DTO;
@using Syncfusion.EJ2.Blazor.Navigations;

@if (navItems != null)
{
    <div>DEFAULT:</div>
    <EjsTreeView TValue="NavItemViewModel">
        <TreeViewFieldsSettings TValue="NavItemViewModel" Id="Id" DataSource="@navItems" Text="Name" ParentID="ParentId" HasChildren="HasChildren" Expanded="Expanded"></TreeViewFieldsSettings>
    </EjsTreeView>

    <div>WITH TEMPLATE:</div>
    <EjsTreeView TValue="NavItemViewModel">
        <TreeViewFieldsSettings TValue="NavItemViewModel" Id="Id" DataSource="@navItems" Text="Name" ParentID="ParentId" HasChildren="HasChildren" Expanded="Expanded" Selected="Selected"></TreeViewFieldsSettings>
        <TreeViewTemplates>
            <NodeTemplate>
                @{
                    var item = context as NavItemViewModel;
                    <span>@item.Name</span>
                }
            </NodeTemplate>
        </TreeViewTemplates>
    </EjsTreeView>

    <div>WITH SIMPLE TEMPLATE:</div>
    <EjsTreeView TValue="NavItemViewModel">
        <TreeViewFieldsSettings TValue="NavItemViewModel" Id="Id" DataSource="@navItems" Text="Name" ParentID="ParentId" HasChildren="HasChildren" Expanded="Expanded" Selected="Selected"></TreeViewFieldsSettings>
        <TreeViewTemplates>
            <NodeTemplate>
                <span>@((context as NavItemViewModel)).Name</span>
            </NodeTemplate>
        </TreeViewTemplates>
    </EjsTreeView>
}
else
{
    <div>Loading...</div>
}

@code {
    protected List<NavItemViewModel> navItems;

    protected override void OnInitialized()
    {
        this.navItems = new List<NavItemViewModel>
{
            new NavItemViewModel
            {
                Id = new Guid("fca52cc4-87ad-4d04-8cb3-6795d27ec5a3"),
                Name = "Reports",
                Type = NavItemType.Container,
                HasChildren = true,
                Position = 0
            },
            new NavItemViewModel
            {
                Id = Guid.NewGuid(),
                Name = "Report 1",
                Type = NavItemType.Report,
                Position = 0,
                ParentId = new Guid("fca52cc4-87ad-4d04-8cb3-6795d27ec5a3")
            }
        };
    }
}