Default term in single select widget should be empty

The default term in single select widget should be empty. Instead, it defaults to the first term which will essentially makes this a required field as they are not able to unselect a term. The same goes for radios.

I had the need for a non-required, single-select widget, so I updated the code. after line 29 ($element['#options'] = $options;), I added this:

$element['#options'] = $options;

Became this:

if ($element['#type'] == 'select') {
  $element['#options'] = _term_reference_filter_by_views_array_unshift_assoc($element['#options'], '', '');
} else if ($element['#type'] == 'radios') {
  $element['#options'] = _term_reference_filter_by_views_array_unshift_assoc($element['#options'], '', 'N/A');
}

I also added a new function so that I could do an array_unshift and keep the index values (term IDs):

/**
 * Array unshift associative
 */
function _term_reference_filter_by_views_array_unshift_assoc(&$arr, $key, $val)  { 
  $arr = array_reverse($arr, true); 
  $arr[$key] = $val; 
  return array_reverse($arr, true); 
}