Provide support for nested properties with null values. 

Currently when using the following scenario: null ref exception is throw, when manager is null:

private Person _manager;
public Person Manager
{
    get { return _manager; }
    set { UpdateValue(ref _manager, value); }
}

<telerik:DataGridTextColumn PropertyName="Manager.Name" 
                            HeaderText="Manager"/>

Provide support for null values when nested properties are used in datagrid columns.

The DataGrid Search As You Type feature provides search text highlighting through the CellContentStyle property of the columns.  

CellContentStyle is taken into account only for the default columns, so when you specify a custom CellContentTemplate or use a TemplateColumn currently the search text highlighting is not applied.