change listeners not fired when SuggestBox cleared from keyboard

[salashnik]

i see some problems in code:

1. delete key not handled anyway :(
2. look in AbstractSuggestBox keyDown.onBackspace code:

....
                  .onBackspace(
                      evt -> {
                        if (!isReadOnly() && !isDisabled()) {
                          if (isNull(getInputStringValue()) || getInputStringValue().isEmpty()) {
                            evt.stopPropagation();
                            evt.preventDefault();
                            onBackspace();
                          }
                        }
                      });
....

getInputString() is not empy in onKeyDown when deleting last character...
our AbstractSuggestBox.onBackspace will be fired only when backspace wil be pressed on empty input
3. SuggestBox.onBackspace code:

    if (nonNull(selectedOption)) {
      selectedOption.remove();
      selectedOption = null;
    }

no any handlers fired :(
as i think onBackspace must simple call clearValue