An extra update has been released for Outlook 2013 and can be downloaded and installed manually, but is also being offered via Microsoft Update.
Update KB2825632 for Outlook 2013
This is a non-security update which has been released to fix the issue where the Folder Pane shows up empty after applying update KB2817630.
View: Download information for KB2825632
If you have Microsoft Update configured to also update other Microsoft applications, then this update will also also be offered via Microsoft Update or has already been updated automatically for you.