[MultiSelectTree] Placeholder is not visible

[georgi-sla]

Describe the bug
Binding the placeholder property does not display a placeholder in the component.

To Reproduce

1. Create a MultiSelectTree component.
2. Bind the placeholder property.
3. Check how the component is rendered.

Please, check out the following StackBlitz demo that demonstrates this issue: https://stackblitz.com/edit/angular-e6652k

Expected behavior
When the placeholder property of the MultiSelectTree is set, the placeholder should be visible in the component.

Screenshots

Additional context
The issue could be reproduced in version 13 of the Kendo packages. In version 12, the placeholder is visible.

Check out the following demo that demonstrates the behavior of the placeholder property with version 12: https://stackblitz.com/edit/angular-ewpmas

[svetq]

This issue will be fixed in the Kendo themes. Please track it at the following link: telerik/kendo-themes#4618