Uncaught (in promise) Error: System.NullReferenceException: Object reference not set to an instance of an object.

I upgraded Telerik UI for Blazor 6.0.2 package from 5.0.0. Now it's erroring on window resizing as:

Uncaught (in promise) Error: System.NullReferenceException: Object reference not set to an instance of an object.
   at Telerik.Blazor.Components.TelerikWindow.SetSize(WindowSizeDescriptor size)
   at Telerik.Blazor.Components.TelerikWindow.Window_ResizeEnd(WindowResizeEventArgs args)
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
   at System.Reflection.MethodBaseInvoker.InvokeDirectByRefWithFewArgs(Object obj, Span`1 copyOfArgs, BindingFlags invokeAttr)
--- End of stack trace from previous location ---
   at Microsoft.JSInterop.Infrastructure.DotNetDispatcher.InvokeSynchronously(JSRuntime jsRuntime, DotNetInvocationInfo& callInfo, IDotNetObjectReference objectReference, String argsJson)
   at Microsoft.JSInterop.Infrastructure.DotNetDispatcher.BeginInvokeDotNet(JSRuntime jsRuntime, DotNetInvocationInfo invocationInfo, String argsJson)
    at y.endInvokeDotNetFromJS (https://localhost:44312/_framework/blazor.server.js:1:3502)
    at Xt._invokeClientMethod (https://localhost:44312/_framework/blazor.server.js:1:61001)
    at Xt._processIncomingData (https://localhost:44312/_framework/blazor.server.js:1:58476)
    at Xt.connection.onreceive (https://localhost:44312/_framework/blazor.server.js:1:52117)
    at s.onmessage (https://localhost:44312/_framework/blazor.server.js:1:80262)

Anyone has any clue?