public function get_instance_option($key, $empty_value = null)
{
if (empty($this->instance_settings)) {
$this->init_instance_settings();
}
// Get option default if unset.
if (!isset($this->instance_settings[$key])) {
$form_fields = $this->get_instance_form_fields();
$this->instance_settings[$key] = $this->get_field_default($form_fields[$key]);
}
if (!is_null($empty_value) && '' === $this->instance_settings[$key]) {
$this->instance_settings[$key] = $empty_value;
}
return $this->instance_settings[$key];
}