Run time error occurs when setting AutoSuggestMode to Suggest only in GridViewComboBoxColumn Editor
Steps to reproduce:

GridViewComboBoxColumn cmb = new GridViewComboBoxColumn(); 
cmb.Name = "Test"; 
cmb.HeaderText = "Test"; 
cmb.DataSource = dt;
cmb.ValueMember = "Id"; 
cmb.DisplayMember = "Name"; 
cmb.FieldName = "Test"; 
cmb.Width = 100;
radGridView1.Columns.Add(cmb);
radGridView1.Columns["Test"].ReadOnly = false;
radGridView1.Columns["Test"].IsVisible = true;
cmb.DropDownStyle = RadDropDownStyle.DropDown;
cmb.AutoCompleteMode = AutoCompleteMode.Suggest;