Neon Dev Unstable Plasma 5.14.8:
Enabling holidays on digital clock causes plasma crash upon Apply.

STEPS TO REPRODUCE
1. Right click on clock
2. Select Digital Clock settings | Calendar
3. Check the Holidays box and click Apply

Plasma crashes immediately and will not restart.

To recover, comment this line in ~/.config/plasma-org.kde.plasma.desktop-appletsrc:
# enabledCalendarPlugins=/usr/lib/x86_64-linux-gnu/qt5/plugins/plasmacalendarplugins/holidaysevents.so


OBSERVED RESULT
Plasmashell crashes and will not restart.  Error thrown:


$ plasmashell &
[1] 4046
darin@imagineNU:~$ org.kde.plasmaquick: Applet preload policy set to 1
file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:61:28: Unable to assign [undefined] to int
file:///usr/share/plasma/plasmoids/org.kde.desktopcontainment/contents/ui/main.qml:52:27: Unable to assign [undefined] to int
trying to show an empty dialog
KActivities: Database connection:  "kactivities_db_resources_139651008317504_readonly" 
    query_only:          QVariant(qlonglong, 1) 
    journal_mode:        QVariant(QString, "wal") 
    wal_autocheckpoint:  QVariant(qlonglong, 100) 
    synchronous:         QVariant(qlonglong, 0)
Closing SQL connection:  "kactivities_db_resources_139651008317504_readonly"
KActivities: Database connection:  "kactivities_db_resources_139651008317504_readonly" 
    query_only:          QVariant(qlonglong, 1) 
    journal_mode:        QVariant(QString, "wal") 
    wal_autocheckpoint:  QVariant(qlonglong, 100) 
    synchronous:         QVariant(qlonglong, 0)
Nothing to load - the client id is empty
Nothing to load - the client id is empty
Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString)
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
r

[1]+  Exit 2                  plasmashell


EXPECTED RESULT
no crashing and holidays on calendar


SOFTWARE/OS VERSIONS
Linux/KDE Plasma:  Yes
(available in About System)
KDE Plasma Version: 5.14.8
KDE Frameworks Version:  5.54.0
Qt Version: 5.11.2

ADDITIONAL INFORMATION