When using the grouped DropDownList and performing a search for a specific element, the DropDownList incorrectly displays the initially shown group instead of the group containing the searched element.

To reproduce the issue: 

1. Open this REPL example: https://blazorrepl.telerik.com/QROrkouK40PFQCUU27
2. Open the DropDownList and type "v" in the filter input field.