O801

If I have non const string parameter like shown in the following sample FI reports an O801 issue.
FI does not seem to see that the parameter is modified in the local funtion.

function TNetCodeProperties.RgbStringToValue(value: String): TColor;

  procedure SkipNoneNumbers;
  begin
    while (value <> '') and not TUnicodeString.IsDigit(value[1]) do
      Delete(value, 1, 1);
  end;

begin
  ...
  SkipNoneNumbers;
  ...
end;