Don't automatically open sidebar when closing all tabs

In my particular workflow, I keep Textastic and Finder open in the same window using Split View, eliminating the need for the sidebar except for folder-level searches. However, when I close all of my active tabs, the sidebar automatically unhides itself, and does not go away when opening new files unless I manually hide it again.

This is certainly a minor issue, but it'd be nice if there were a setting I could toggle to disable this feature so the sidebar doesn't automatically show unless I manually show it.