Bricked part of the toolbar

[AellaCarina]

I deleted a blueprint from my library. That blueprint was also stored in the toolbar. Now I have a red "X" in the toolbar that I can't remove or replace with something else. Anytime I try to do something with that square in the toolbar I receive the message

"Target of this shortcut to the blueprint library is no longer present."

HELP!

[Koub]

Try Middle-clicling (clicking with your mousewheel) on the red cross.