Source

File: wp-includes/customize/class-wp-customize-nav-menu-item-setting.php

public function value() {
		if ( $this->is_previewed && get_current_blog_id() === $this->_previewed_blog_id ) {
			$undefined  = new stdClass(); // Symbol.
			$post_value = $this->post_value( $undefined );

			if ( $undefined === $post_value ) {
				$value = $this->_original_value;
			} else {
				$value = $post_value;
			}
			if ( ! empty( $value ) && empty( $value['original_title'] ) ) {
				$value['original_title'] = $this->get_original_title( (object) $value );
			}
		} elseif ( isset( $this->value ) ) {
			$value = $this->value;
		} else {
			$value = false;

			// Note that a ID of less than one indicates a nav_menu not yet inserted.
			if ( $this->post_id > 0 ) {
				$post = get_post( $this->post_id );
				if ( $post && self::POST_TYPE === $post->post_type ) {
					$is_title_empty = empty( $post->post_title );
					$value          = (array) wp_setup_nav_menu_item( $post );
					if ( $is_title_empty ) {
						$value['title'] = '';
					}
				}
			}

			if ( ! is_array( $value ) ) {
				$value = $this->default;
			}

			// Cache the value for future calls to avoid having to re-call wp_setup_nav_menu_item().
			$this->value = $value;
			$this->populate_value();
			$value = $this->value;
		}

		if ( ! empty( $value ) && empty( $value['type_label'] ) ) {
			$value['type_label'] = $this->get_type_label( (object) $value );
		}

		return $value;
	}