src/class-upgrader.php
protected function prepare_ignored_themes( array $themes ) {
		$valid_slugs = array_values( wp_list_pluck(
			wp_get_themes(),
			'stylesheet'
		) );

		return array_values( array_intersect( $valid_slugs, $themes ) );
	}
protected function prepare_ignored_themes( array $themes ) {
		$valid_slugs = array_values( wp_list_pluck(
			wp_get_themes(),
			'stylesheet'
		) );

		return array_values( array_intersect( $valid_slugs, $themes ) );
	}
protected function prepare_ignored_themes ( array $ themes ) { $ valid_slugs = array_values ( wp_list_pluck ( wp_get_themes ( ) , 'stylesheet' ) ) ; return array_values ( array_intersect ( $ valid_slugs , $ themes ) ) ; }
Ensure ignored themes setting only contains currently installed themes.

@param  array $themes List of ignored themes.

@return array
Ensure ignored themes setting only contains currently installed themes .