Pressing super key brings up menu with no way to make it go away

If I accidentally press the Super key (or Windows key), it apparently goes into some kind of Overview format and shows a window of commands that could be typed. It's a pretty dark black window (just barely translucent) and takes up most of the screen.

The problem is that the window won't go away once it shows up. Pressing the Super key again repeatedly does not make it go away. Waiting does not make it go away. Pressing escape, or hitting control q or hitting control c does not make it go away. The only thing I've figured out how to do is reboot the computer which is extremely inconvenient.

It seems to be a bug.

1) Ubuntu version 18.04.2 LTS
2) ubuntu-bug wants to know what package and I don't know how to figure out what package that is. All I know is it's the super key. I tried gnomu-unity and gnome and it said no packages matching gnome.
3) what I expected to happen is having some way to make the menu go away again (probably by continuing to press the Super key a couple more times) or by pressing Esc... but it does not go away unless I reboot the computer.
4) what happened instead is see above. I tried various things to make it go away and none of them worked.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: gnome (not installed)
ProcVersionSignature: Ubuntu 4.15.0-46.49-generic 4.15.18
Uname: Linux 4.15.0-46-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sat Mar 30 12:27:34 2019
InstallationDate: Installed on 2018-12-01 (118 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: meta-gnome3
UpgradeStatus: No upgrade log present (probably fresh install)