missing "Tool Controls Bar" in Inkscape alpha

Windows 10, Inkscape 1.0alpha2 (7068dfd, 2019-06-13)

• start Inkscape, note that the Tool Controls Bar is present

• hit any other F key, other than F1, and the Tool Controls Bar disappears

• hit F1 and it reappears

• hit any other F key and it disappears

• not reproduced on Inkscape 0.92.4 (5bc3bdf, 2019-06-08)