Cron runs prematurely when installing an installation profile that includes this module.

This is related to https://www.drupal.org/node/2701115 and may not be of much interest to anyone else.

It seems when installing a site using an installation profile the cron hook that tries to set/get site metadata from Solr is fired before the default search environment is set. I realise this is probably an edge case, but I need to get rid of errors in our build system.