Hidden tab can be opened in the logger's window, so closing it generates a prompt

[enomat]

1. Open the logger in a new window (shift+click).
2. Load any page, so items will appear in the logger.
3. Click on the 2. column, so the popup UI will appear in the logger.
4. Click on the Ublock name/version which opens Ublock's settings menu.

The settings menu will be opened in a new tab in the logger's window. That tab cannot be closed (because the tab bar is hidden). So if you want to close the logger's window, a prompt will appear which says 2 tabs wil be closed and asks if you want to continue.
( Firefox 38.0.5 with UBlock Origin 1.0.0.0 )

[luxoflux]

Confirmed.

Though personally, I just open the logger normally and drag the tab out to separate it.

[gorhill]

This was fixed at some point, the tab bar and other toolbars are no longer hidden when the logger is opened in a separate window.