Launcher exits when closing a log window

Steps to reproduce:

• Open the launcher
• In Settings > General:
• check Keep the Launcher open while games are running
• check Open output log when games start
• Launch a Minecraft instance
• Close the log window which opened

What I expected:
The log window should close, and the main launcher window should stay open.

What happened
The log window and the main launcher window both closed. I have to restart the launcher entirely.