Spectacle Closes Unexpectedly When Screenshot Notifications Close

[Harley A.W. Lorenzo]

If a screenshot notification closes while the spectacle window is open, the spectacle window will close unexpectedly.

Steps to reproduce:
1. Take a screenshot via a hotkey (so the spectacle notification appears)
2. Open spectacle so the main window appears
3. Close the notification (or wait for it to automatically close) and watch as the spectacle window, which is unrelated to the screenshot notification, close because of the screenshot notification

Expected behavior: Spectacle window unaffected by other screenshot notifications closing

ProblemType: Bug
DistroRelease: Ubuntu 19.04
Package: kde-spectacle 18.12.3-0ubuntu1
ProcVersionSignature: Ubuntu 5.0.0-8.9-generic 5.0.1
Uname: Linux 5.0.0-8-generic x86_64
ApportVersion: 2.20.10-0ubuntu26
Architecture: amd64
CurrentDesktop: KDE
Date: Tue Apr 9 18:39:33 2019
ExecutablePath: /usr/bin/spectacle
InstallationDate: Installed on 2019-04-08 (1 days ago)
InstallationMedia: Kubuntu 19.04 "Disco Dingo" - Alpha amd64 (20190326.1)
ProcEnviron:
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: kde-spectacle
UpgradeStatus: No upgrade log present (probably fresh install)