if( ( ix == 0 && offset == -1 ) || ( ix == items.size() - 1 && offset == 1 ) )
{
return;
}
assertion.removePropertyChangeListener( this );
items.remove( ix );
fireIntervalRemoved( this, ix, ix );
// remove associated errors
while( ix < items.size() && items.get( ix ) instanceof AssertionError )