When trying to tail a empty capped collection, the won't work.

So now to make this work I have to insert a dummy document, but I don't think this should be necessary?

The issue is mentioned in a comment before, almost 3 years ago:
https://jira.mongodb.org/browse/RUBY-534?focusedCommentId=253604&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-253604