STEPS TO REPRODUCE
1. Under default applications select: /usr/bin/thunderbird
2. Hover over "KDE Docs Team" in helpcenter 

OBSERVED RESULT
As soon as I hover over "KDE Docs Team", helpcenter crashes.
However on X11 it prints:
"Unable to create io-slave. klauncher said: Unknown protocol 'mailto'." 

EXPECTED RESULT

It prints an error like on X11

SOFTWARE/OS VERSIONS

Operating System: openSUSE Tumbleweed 20200819
KDE Plasma Version: 5.19.4
KDE Frameworks Version: 5.73.0
Qt Version: 5.15.0
Kernel Version: 5.8.0-1-default
OS Type: 64-bit

ADDITIONAL INFORMATION

Application: Help Center (khelpcenter), signal: Segmentation fault

[KCrash Handler]
#4  0x00007f0fb5293142 in XChangeWindowAttributes (dpy=0x557b9ce7e640, w=w@entry=2, valuemask=valuemask@entry=1024, attributes=attributes@entry=0x7ffe449d5a70) at ChWAttrs.c:47
#5  0x00007f0fb7662f6d in KHTMLView::mouseMoveEvent (this=0x557b9cf96a70, _mouse=0x7ffe449d6100) at /usr/src/debug/khtml-5.73.0-1.1.x86_64/src/khtmlview.cpp:1539
#6  0x00007f0fb67190de in QWidget::event (this=this@entry=0x557b9cf96a70, event=event@entry=0x7ffe449d6100) at kernel/qwidget.cpp:9027
#7  0x00007f0fb67c14de in QFrame::event (this=0x557b9cf96a70, e=0x7ffe449d6100) at widgets/qframe.cpp:550
#8  0x00007f0fb765e6d4 in KHTMLView::eventFilter (this=0x557b9cf96a70, o=0x557b9d2eaf30, e=0x7ffe449d6100) at /usr/src/debug/khtml-5.73.0-1.1.x86_64/src/khtmlview.cpp:2115
#9  0x00007f0fb5a69983 in QCoreApplicationPrivate::sendThroughObjectEventFilters (event=<optimized out>, receiver=<optimized out>) at kernel/qcoreapplication.cpp:1187
#10 QCoreApplicationPrivate::sendThroughObjectEventFilters (receiver=receiver@entry=0x557b9d2eaf30, event=event@entry=0x7ffe449d6100) at kernel/qcoreapplication.cpp:1176
#11 0x00007f0fb66d90be in QApplicationPrivate::notify_helper (this=this@entry=0x557b9ce63c00, receiver=receiver@entry=0x557b9d2eaf30, e=e@entry=0x7ffe449d6100) at kernel/qapplication.cpp:3665
#12 0x00007f0fb66e0121 in QApplication::notify (this=0x7ffe449d5e00, receiver=0x557b9d2eaf30, e=0x7ffe449d6100) at kernel/qapplication.cpp:3115
#13 0x00007f0fb5a69c1a in QCoreApplication::notifyInternal2 (receiver=0x557b9d2eaf30, event=0x7ffe449d6100) at ../../include/QtCore/5.15.0/QtCore/private/../../../../../src/corelib/thread/qthread_p.h:325
#14 0x00007f0fb66df036 in QApplicationPrivate::sendMouseEvent (receiver=receiver@entry=0x557b9d2eaf30, event=event@entry=0x7ffe449d6100, alienWidget=alienWidget@entry=0x557b9d2eaf30, nativeWidget=0x557b9cf1d0b0, buttonDown=buttonDown@entry=0x7f0fb6bfe9d0 <qt_button_down>, lastMouseReceiver=..., spontaneous=true, onlyDispatchEnterLeave=false) at kernel/qapplication.cpp:2603
#15 0x00007f0fb673113a in QWidgetWindow::handleMouseEvent (this=0x557b9d21e190, event=0x7ffe449d63c0) at /usr/include/c++/10/bits/atomic_base.h:420
#16 0x00007f0fb673462e in QWidgetWindow::event (this=0x557b9d21e190, event=0x7ffe449d63c0) at kernel/qwidgetwindow.cpp:295
#17 0x00007f0fb66d90cf in QApplicationPrivate::notify_helper (this=<optimized out>, receiver=0x557b9d21e190, e=0x7ffe449d63c0) at kernel/qapplication.cpp:3671
#18 0x00007f0fb5a69c1a in QCoreApplication::notifyInternal2 (receiver=0x557b9d21e190, event=0x7ffe449d63c0) at ../../include/QtCore/5.15.0/QtCore/private/../../../../../src/corelib/thread/qthread_p.h:325
#19 0x00007f0fb5fc227b in QGuiApplicationPrivate::processMouseEvent (e=0x557b9d1e0370) at kernel/qguiapplication.cpp:2214
#20 0x00007f0fb5f9851b in QWindowSystemInterface::sendWindowSystemEvents (flags=...) at kernel/qwindowsysteminterface.cpp:1175
#21 0x00007f0fb10e7880 in userEventSourceDispatch (source=<optimized out>) at qeventdispatcher_glib.cpp:74
#22 0x00007f0fb3b552b7 in g_main_context_dispatch () from /usr/lib64/libglib-2.0.so.0
#23 0x00007f0fb3b55638 in ?? () from /usr/lib64/libglib-2.0.so.0
#24 0x00007f0fb3b556ef in g_main_context_iteration () from /usr/lib64/libglib-2.0.so.0
#25 0x00007f0fb5ac105f in QEventDispatcherGlib::processEvents (this=0x557b9cef4810, flags=...) at kernel/qeventdispatcher_glib.cpp:423
#26 0x00007f0fb5a685db in QEventLoop::exec (this=this@entry=0x7ffe449d66f0, flags=..., flags@entry=...) at ../../include/QtCore/../../src/corelib/global/qflags.h:141
#27 0x00007f0fb5a70840 in QCoreApplication::exec () at ../../include/QtCore/../../src/corelib/global/qflags.h:121
#28 0x00007f0fb5fb5a8c in QGuiApplication::exec () at kernel/qguiapplication.cpp:1867
#29 0x00007f0fb66d9045 in QApplication::exec () at kernel/qapplication.cpp:2811
#30 0x00007f0fb7cfdcd1 in kdemain (argc=<optimized out>, argv=<optimized out>) at /usr/src/debug/khelpcenter5-20.08.0-1.1.x86_64/application.cpp:124
#31 0x00007f0fb7b17cca in __libc_start_main () from /lib64/libc.so.6
#32 0x0000557b9b62608a in _start () at ../sysdeps/x86_64/start.S:120
[Inferior 1 (process 13569) detached]