/**
	 * Returns the change that should be processed.
	 *
	 * EntityChange objects are loaded using a EntityChangeLookup.
	 *
	 * @return EntityChange|null the change to process (or none).
	 */
	private function getChange(): ?EntityChange {
		$params = $this->getParams();
		$change = $this->changeFactory->newFromFieldData( $params['change'] );

		// If the current change was composed of other child changes, restore the
		// child objects.
		$info = $change->getInfo();
		if ( isset( $info['change-ids'] ) && !isset( $info['changes'] ) ) {
			$children = $this->changeLookup->loadByChangeIds( $info['change-ids'] );
			$info['changes'] = $children;
			$change->setField( ChangeRow::INFO, $info );
		}

		return $change;
	}