Grid Grouping - Null vs Empty String

We noticed that when grouping on columns that sometimes have a null and sometimes have an empty string, it will create two different groupings.

I tried to update the ViewModel in MVC so the property always returns an empty string:

public class SampleViewModel
{    
    private string _name;        
   
    [StringLength(50)]
    public string Name    
    {        
        get { return _name ?? string.Empty; }        
        set { _name= value; }    
    }
}

That still produces two different groupings.

How can I get the grid to group these the same way?