Oleksandr Hotsaliuk

PriceListTreeHandler TypeErrors fix in case when `Oro\Bundle\WebsiteBundle\Manager\WebsiteManager::getCurrentWebsite` returns `null` value. Related to https://github.com/oroinc/orocommerce/issues/118

The method requires `Website` object, but annotation said it could be null https://github.com/oroinc/orocommerce/blob/164950cbf7cf96d11e58ba3c9e7ac28e37fa4ce5/src/Oro/Bundle/PricingBundle/Model/PriceListTreeHandler.php#L142 https://github.com/oroinc/orocommerce/blob/164950cbf7cf96d11e58ba3c9e7ac28e37fa4ce5/src/Oro/Bundle/PricingBundle/Model/PriceListTreeHandler.php#L145 Couse TypeError exception from the `getPriceList` method when it's both attributes nullable.