Wikimedia Bugzilla is closed!

Obviously it is a typo in current SVN sources:

		if ( !is_null( $this->m_property ) ) {
			$propertyDiWikiPage = $this->m_property->getDiWikiPage();
		}
		if ( is_null( $this->m_property ) || is_null( $propertyDiWikiPag <<<--- Look here ) ) {
			return; // we cannot find conversion factors without the property
		}