Similar to KDEBUG 390060 and - maybe - 389978.
System: Arch Linux (with some modifications), KF5.43rc1 (not in repository), Plasma 5.12.0, amdgpu for Sea Islands with DC, linux 4.15.1.

Bug occours only in Icon View (Tree and Sidebar View aren't affected). When I try to select Night Color, systemsettings closes suddenly.

Only useful output in gdb is:
"[New Thread 0x7fffe269e700 (LWP 19481)]
Using Wayland-EGL
[New Thread 0x7fffd1122700 (LWP 19482)]
[New Thread 0x7fffcbfff700 (LWP 19483)]
[New Thread 0x7fffcb7fe700 (LWP 19484)]
[New Thread 0x7fffcaffd700 (LWP 19485)]
[New Thread 0x7fffca7fc700 (LWP 19486)]
[New Thread 0x7fffc9ffb700 (LWP 19487)]
[New Thread 0x7fffc97fa700 (LWP 19488)]
Using the 'xdg-shell-v6' shell integration
[New Thread 0x7fffb275a700 (LWP 19490)]
kscreen.kwayland: Loading Wayland backend.
[New Thread 0x7fffb1f59700 (LWP 19491)]
[New Thread 0x7fffb1758700 (LWP 19492)]
[New Thread 0x7fff9da0d700 (LWP 19493)]
[New Thread 0x7fff9d20c700 (LWP 19494)]
org.kde.kcoreaddons: Error loading plugin "kcm_nightcolor" "The shared library was not found." 
Plugin search paths are ("/usr/lib/qt/plugins", "/usr/bin") 
The environment variable QT_PLUGIN_PATH might be not correctly set
[New Thread 0x7fff97fff700 (LWP 19495)]
networkmanager-qt: void NetworkManager::NetworkManagerPrivate::propertiesChanged(const QVariantMap&) Unhandled property "AllDevices"
networkmanager-qt: void NetworkManager::NetworkManagerPrivate::propertiesChanged(const QVariantMap&) Unhandled property "Capabilities"
networkmanager-qt: void NetworkManager::NetworkManagerPrivate::propertiesChanged(const QVariantMap&) Unhandled property "ConnectivityCheckAvailable"
networkmanager-qt: void NetworkManager::NetworkManagerPrivate::propertiesChanged(const QVariantMap&) Unhandled property "ConnectivityCheckEnabled"
networkmanager-qt: void NetworkManager::NetworkManagerPrivate::propertiesChanged(const QVariantMap&) Unhandled property "Devices"
networkmanager-qt: void NetworkManager::NetworkManagerPrivate::propertiesChanged(const QVariantMap&) Unhandled property "GlobalDnsConfiguration"
gpsd not found
"location"
Fetching https://location.services.mozilla.com/v1/geolocate
Trying to use rootObject before initialization is completed, whilst using setInitializationDelayed. Forcing completion
wl_display@1: error 0: invalid object 89
The Wayland connection experienced a fatal error (Invalid argument)
[Thread 0x7fff9da0d700 (LWP 19493) exited]
[Thread 0x7fffc9ffb700 (LWP 19487) exited]
[Thread 0x7fffca7fc700 (LWP 19486) exited]
[Thread 0x7fffcaffd700 (LWP 19485) exited]
[Thread 0x7fffcb7fe700 (LWP 19484) exited]
[Thread 0x7fffd1122700 (LWP 19482) exited]
[Thread 0x7fffcbfff700 (LWP 19483) exited]
[Thread 0x7fffc97fa700 (LWP 19488) exited]
[Thread 0x7fffe269e700 (LWP 19481) exited]
[Thread 0x7fff97fff700 (LWP 19495) exited]
[Thread 0x7fff9d20c700 (LWP 19494) exited]
[Thread 0x7fffb1758700 (LWP 19492) exited]
[Thread 0x7fffb1f59700 (LWP 19491) exited]
[Thread 0x7ffff7f8d800 (LWP 19480) exited]
[Inferior 1 (process 19480) exited with code 01]"
There are some info related to networkmanager or geolocate, but I think isn't related to this bug. I left them in output.