Splitter bar in a tabbed conversation window doesn't appear after it's resized to minimum in Skype for Business 2016

Symptoms

When you resize the splitter bar to the minimum size in a tabbed conversation window in Microsoft Skype for Business 2016, the splitter bar disappears.

Resolution

To fix this issue, install the November 13, 2018, security update for Skype for Business 2016 (KB4461473).