Recommend Updates email doesn't send with "doSend Summary email does not have content for user" in 5.4.3

Steps to Replicate:

1. Enable DEBUG logging on the package: com.atlassian.confluence.plugins.dailysummary
2. Leave Confluence running for either a whole day, or change one of your user's timezones so that it's 1pm their time (as running Recommended Updates Email task on Scheduled Jobs does nothing unless it's 1pm) and run the task via Confluence Admin > Scheduled Jobs)

Even if there is recent content, the email will not send, and the following is seen in the logs:

2014-09-10 10:00:00,442 DEBUG [scheduler_Worker-9] [dailysummary.components.impl.DefaultSummaryEmailService] doSend Summary email does not have content for user com.atlassian.confluence.user.ConfluenceUserImpl@929218d[admin,4028808544b514fb0144b517049d0003]