Hmm, a blank Bookmarks Toolbar isn't very useful, unless you have other things you want to use it for. To hide the blank bar, try the steps in the following article:

Bookmarks Toolbar - Display your favorite websites at the top of the Firefox window (first section is "Show or hide the Bookmarks toolbar")

Does that take care of it?

Hmm, a blank Bookmarks Toolbar isn't very useful, unless you have other things you want to use it for. To hide the blank bar, try the steps in the following article: Bookmarks Toolbar - Display your favorite websites at the top of the Firefox window (first section is "Show or hide the Bookmarks toolbar") Does that take care of it?

I don't need to hide it. In the Bookmarks Toolbar I have only 3 bookmarks and everything else in my Bookmarks Menu. It's more convenient for me when the most important bookmarks are at hand and all the trash is on the menu

But in your screenshot it looks like you customized the toolbars, moving "Bookmarks Toolbar Items" from the Bookmarks Toolbar to your main toolbar, leaving the physical Bookmarks Toolbar empty. I guess you could double-check on that using Customize:

Customize Firefox controls, buttons and toolbars