Merge pull request #624 in ZP/z-push from bugfix/ZP-1324-carddav-message-asbody-data-null to develop

* commit 'ea955f4b':
  ZP-1324 Review comment. Released under the Affero GNU General Public License (AGPL) version 3.
  ZP-1324 Carddav, $message->asbody->data can be NULL. Released under the Affero GNU General Public License (AGPL) version 3.