LB-545: Embed URL crashes if a user who has published posts is deleted

This is a wrong PR (against master). The next one is the right one (against devel).

adjusted with Active/Inactive users. see the comment by the jira issue

http://dev.sourcefabric.org/browse/LB-545?focusedCommentId=37105&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-37105