Crash on viewspace close
Start Kate, split, open welcome page in second viewspace, close that viewspace:
(gdb) bt
#0 0x00007ffff639bf94 in QWidget::layout() const () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Widgets.so.5
#1 0x00007ffff63914b8 in QLayout::addChildWidget(QWidget*) () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Widgets.so.5
#2 0x00007ffff63979fd in QStackedLayout::insertWidget(int, QWidget*) () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Widgets.so.5
#3 0x00007ffff7ede787 in KateViewSpace::addWidgetAsTab (this=0x128d1a0, widget=0x19262d0) at /home/cullmann/projects/kde/src/kate/apps/lib/kateviewspace.cpp:864
#4 0x00007ffff7ed67f6 in KateViewManager::removeViewSpace (this=0xba2330, viewspace=<optimized out>) at /home/cullmann/projects/kde/src/kate/apps/lib/kateviewmanager.cpp:1467
#5 0x00007ffff54f68f0 in QObject::event(QEvent*) () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Core.so.5
#6 0x00007ffff645e6be in QFrame::event(QEvent*) () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Widgets.so.5
#7 0x00007ffff637105e in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Widgets.so.5
#8 0x00007ffff54ca878 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Core.so.5
#9 0x00007ffff54cd8b1 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Core.so.5
#10 0x00007ffff5523273 in postEventSourceDispatch(_GSource*, int (*)(void*), void*) () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Core.so.5
#11 0x00007ffff3715ead in g_main_context_dispatch () from /nix/store/5gs8a87g7dfy1pgylzc7bgri68fd8a66-glib-2.76.4/lib/libglib-2.0.so.0
#12 0x00007ffff3716158 in g_main_context_iterate.constprop () from /nix/store/5gs8a87g7dfy1pgylzc7bgri68fd8a66-glib-2.76.4/lib/libglib-2.0.so.0
#13 0x00007ffff37161ec in g_main_context_iteration () from /nix/store/5gs8a87g7dfy1pgylzc7bgri68fd8a66-glib-2.76.4/lib/libglib-2.0.so.0
#14 0x00007ffff5522a56 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Core.so.5
#15 0x00007ffff54c9273 in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Core.so.5
#16 0x00007ffff54d1776 in QCoreApplication::exec() () from /nix/store/w0rqvc39zhlv1b633zim1rwva0hbij85-qtbase-5.15.9/lib/libQt5Core.so.5
#17 0x0000000000409e58 in main (argc=<optimized out>, argv=<optimized out>) at /home/cullmann/projects/kde/src/kate/apps/kate/main.cpp:609