Error when clearing dropdown with delete key when DisabledProperty is entered

[bert-algoet]

Describe the bug
When passing the DisabledProperty to the RadzenDropDown, pressing delete on a dropdown to clear it results in an error.
This is because the disabledPropertyGetter(item) does not support null as a parameter.

To Reproduce
<RadzenDropDown TValue="SomeClassWithIsDisabledProperty"
Data="@_lst"
DisabledProperty="IsDisabled"
AllowClear="true"
@bind-Value="@_selectedItem">

Select an item and then press delete.