Flashbulb graphics effect gets screen stuck completely black

[Chai T. Rex]

 Release used
==============

Description: Ubuntu 16.04.3 LTS
Release: 16.04

 Package version used
======================

gnome-screenshot:
  Installed: 3.18.0-1ubuntu2
  Candidate: 3.18.0-1ubuntu2
  Version table:
 *** 3.18.0-1ubuntu2 500
        500 http://mirror.atlantic.net/ubuntu xenial/main amd64 Packages
        100 /var/lib/dpkg/status

 What was expected
===================

When taking a screenshot with GNOME Screenshot by pressing the PrtScr button, the screen will have a flashbulb graphics effect, where the screen gets bright white, then black, then back to normal.

 What happened instead
=======================

The flashbulb graphics effect went to black and stopped there, leaving the GUI unusable and forcing me to reboot to get things back to normal.

This didn't happen before my upgrade today from a 4.10 kernel to a 4.13 kernel (specifically 4.13.0-26.29~16.04.2), so that may be related.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: gnome-screenshot 3.18.0-1ubuntu2
ProcVersionSignature: Ubuntu 4.13.0-26.29~16.04.2-generic 4.13.13
Uname: Linux 4.13.0-26-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.15
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Jan 10 17:43:54 2018
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-xenial-amd64-20160624-2
EcryptfsInUse: Yes
InstallationDate: Installed on 2016-11-01 (435 days ago)
InstallationMedia: Ubuntu 16.04 "Xenial" - Build amd64 LIVE Binary 20160624-10:47
JournalErrors:
 Error: command ['journalctl', '-b', '--priority=warning', '--lines=1000'] failed with exit code 1: Hint: You are currently not seeing messages from other users and the system.
       Users in the 'systemd-journal' group can see all messages. Pass -q to
       turn off this notice.
 No journal files were opened due to insufficient permissions.
SourcePackage: gnome-screenshot
UpgradeStatus: No upgrade log present (probably fresh install)

[Chai T. Rex (chaitrex)]

It appears that the following is better than a reboot:

1. Press Ctrl+Alt+F3
2. Log in
3. Run `killall gnome-screenshot`
4. Press Ctrl+Alt+F7 (or Ctrl+Alt+F2 if that doesn't get you back to the GUI)