- Create a new site template from SharePoint Designer. Doesn't really matter what the site template is for or what options you choose (based on my experience).
- Go into SharePoint and create a new site based on the new custom Site Template.
- Note that your top navigation bar (the global navigation) should now have a "Home" tab, and an "Error" tab.
- Click refresh.
- Your top navigation bar now appears as normal!
I'll chalk this one up as a "feature".