void removeListeners() {
if (isValid()) {
proposalTable.removeListener(SWT.FocusOut, this);
ScrollBar scrollbar = proposalTable.getVerticalBar();
if (scrollbar != null) {
scrollbar.removeListener(SWT.Selection, this);
}
getShell().removeListener(SWT.Deactivate, this);
getShell().removeListener(SWT.Close, this);
}