GlobarDrawer has unusually shaped scrollable area

This binding right here:

c3e00e58

        QQC2.ScrollBar.vertical.anchors {
            top: scrollView.top
            bottom: scrollView.bottom
            topMargin: headerParent.height + headerParent.y

it causes scrollable area of a drawer to be shaped like this:

I see two problems with this.

First, it interferes with whatever scrolling handling of a header itself without actually causing said header to scroll away anywhere.

Second, just what the hail is that notch on the top right?