Cursor disappears after capture and release

[Nathaniel W. Turner]

Steps:
1. Open a VM window
2. Click in the VM window. The cursor will be "captured" and disappear, and the window title will indicate "Press Control-L+Alt_L to release pointer."
3. Press Press Control-L+Alt_L.

Expected result:
- The pointer is "released" and reappears.

Actual result:
- The pointer is "released", but remains invisible when pointing at any virt-manager window.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: virt-manager 1:1.5.0-0ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-13.14-generic 4.15.10
Uname: Linux 4.15.0-13-generic x86_64
ApportVersion: 2.20.9-0ubuntu2
Architecture: amd64
CurrentDesktop: GNOME
Date: Wed Apr 11 11:31:00 2018
EcryptfsInUse: Yes
PackageArchitecture: all
SourcePackage: virt-manager
UpgradeStatus: Upgraded to bionic on 2018-03-06 (35 days ago)