D11891: Fix crashes in NotifyByAudio when closing applications

[Aleix Pol Gonzalez]

apol accepted this revision.

REPOSITORY
  R289 KNotifications

REVISION DETAIL
  https://phabricator.kde.org/D11891

To: aacid, #frameworks, cullmann, rjvbb, apol
Cc: cfeck, rjvbb, mpyne, michaelh, ngraham, bruns