Adding a cancel button to the creating Library Loading Bar

[Thesacraft]

Hi, I think it would be useful if you added a cancel button in the "Refreshing Directories" Window, that pops up after creating a new Library. Because at this point of time a miss selection of a whole drive as a new Library, can't be canceled (at least i have not found a way to do it) and it would be tedious to restart the whole application. Iit would also be an option to add this functionality to the closing button of the popup.