Missing toString method passing an object as kendo.Observable

[aleksandarevangelatov]

Bug report

If an object has an overridden toString method and is passed as a kendo.Observable the toString method of the object is not passed. This is a regression introduced with v2020.3.1023.

Reproduction of the problem

1. Run this dojo
2. The overriden toString method is not available

Expected/desired behavior

The custom toString method should be passed, as in v2020.3.915: dojo

Environment

• Kendo UI version: 2021.1.224
• Browser: [all]

[martintabakov]

The issue persist when using prototype to override the toString method. Refer to this example - https://dojo.telerik.com/EpemoliS.
It works fine with version 2020.3.915.

[veselints]

Related to: #5973

[veselints]

A similar issue is also present when assigning a jQuery object to a field in the observable. Here is a Dojo demonstrating the result:
https://dojo.telerik.com/eyeHosEQ/3

[Iankodj]

Dojo to test #5973: https://dojo.telerik.com/@iankodj/EBIguToM