Filtering ADOTable error - "could not convert type Null to type OleStr"

Question

I am trying to filter an ADOTable for records with a field 'OwnerName' value matches the one in a edit on my GUI component. When entering a name that does not exist, i get the above mentioned error. When there are no names in the database that match the filter, I just want the dbgrid to display nothing, how can this be done? Still a noob, so could anyone enlighten me?

Code used:

procedure TOwners.edt_Name_FilterChange(Sender: TObject);
begin
  Filter;
end;
//-----------------------------------------------------------
procedure TOwners.Filter;
begin
  if edt_Name_Filter.text = '' then
  begin
    CarOwners.tbl_Owners.Filtered := false;
    exit;
  end;

  with CarOwners do
  begin
    tbl_Owners.Filtered := false;
    tbl_Owners.Filter := 'OwnerName LIKE ''' + '%' + edt_Name_Filter.text +
      '%' + '''';
  if tbl_owners['OwnerName'] = null then
  begin
    tbl_owners.filter := '';
  end;
    tbl_Owners.Filtered := true;
  end;
end;