Video Editor "Add" Dialog - Problems with Closing

In the 'Add' dialog in the video editor, (1) the upper right 'x' to close the window looks odd - the x is too low, and far to the right of the wide button, (2) the 'back' button is disabled, and (3) pressing the escape key doesn't close the dialog.

As a consequence, it took me a while to figure out how to cancel and close the window, as the only functioning way to close it - the 'x' - looks odd, and the other ways I tried (pressing the escape key and 'back' button) don't work.