With flatpak applications we can have the following scenario:
appId= "org.kde.ark.kdbus-_1_769" newAppId= "org.kde.ark.kdbus" pendingAppId= "org.kde.ark"
because of https://phabricator.kde.org/D5775
This breaks matchesPendingRequest(), resulting in an annoying
"KDEInit could not launch '/usr/bin/flatpak'" dialog after closing the app.
This patch adds an explicit check for this case.