plasma wayland crashes after login, ksplashqml SIGSEGV

[Starrah]

I install KDE plasma with both X11(plasma-workspace, builtin with KUbuntu22.04) and Wayland(by manually installing plasma-workspace-wayland). The plasma with X11 is all good, but for plasma with Wayland, after logging in from sddm, the background is black with only one error dialog "We are sorry, ksplasqml closed unexpectedly", and the error is SIGSEGV.

Environment:
Plasma workspace: 5.24.7 (plasma-workspace-wayland: 4:5.24.7-0ubuntu0.1)
OS: KUbuntu 22.04
CPU: Intel i7-12700K
GPU: NVIDIA 2080Ti with official driver 535.113.01

By debugging with GDB, the backtrace of SIGSEGV is
Thread 1 "ksplashqml" received signal SIGSEGV, Segmentation fault.
0x00007ffff6eea25b in QObject::setProperty(char const*, QVariant const&) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
(gdb) backtrace
#0 0x00007ffff6eea25b in QObject::setProperty(char const*, QVariant const&) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
#1 0x000055555555aee9 in SplashWindow::setStage (this=this@entry=0x7fffec010300, stage=0) at ./ksplash/ksplashqml/splashwindow.cpp:75
#2 0x00005555555598e4 in SplashApp::adoptScreen (this=this@entry=0x7fffffffd720, screen=0x555555590290) at ./ksplash/ksplashqml/splashapp.cpp:137
#3 0x000055555555a0ef in SplashApp::SplashApp (this=this@entry=0x7fffffffd720, argc=@0x7fffffffd71c: 2, argv=argv@entry=0x7fffffffd898)
    at ./ksplash/ksplashqml/splashapp.cpp:74
#4 0x0000555555558db5 in main (argc=<optimized out>, argv=0x7fffffffd898) at ./ksplash/ksplashqml/main.cpp:60

The function SplashWindow::setStage in `ksplash/ksplashqml/splashwindow.cpp` is:
void SplashWindow::setStage(int stage) {
    m_stage = stage;
    rootObject()->setProperty("stage", stage); // Line 75
}

With further debugging, I found that `rootObject()` returned a NULL pointer, which causes the SIGSEGV.

[Scarlett Gately Moore (scarlettmoore)]

Please enable backports and update and tell me if this is still an issue.