[function.array-key-exists] hatası

Warning: array_key_exists() [function.array-key-exists]: The first argument should be either a string or an integer in /public_html/wp-includes/cache.php on line 618

protected function _exists( $key, $group ) {
		return isset( $this->cache[ $group ] ) && ( isset( $this->cache[ $group ][ $key ] ) || array_key_exists( $key, $this->cache[ $group ] ) );
	}