Buster+Gnome on Pi4

[pcr <pcr@pcrt.us>]

Recently I flashed the 20200210 build of debian to a 128 GB A2 SanDisk 
micro sd card and I have been using in in in my raspberry pi.  I 
recently lost my desktop to a crash, so I am temporarily relying on the 
Pi.  So far it pretty good, about as fast as my old i3 laptop; one bug, 
however, is a black rectangle that appears on the middle of my screen 
occasionally.  It goes away if I right click-left click, or if I waggle 
the mouse pointer over the black rectangle, so it remains usable.  Ill 
let you know how it goes.