This is the backtrace:

0  0x00007ffff38a11cc in KoColorSet::getGroup(QString const&) () from
/usr/lib64/libkritapigment.so.18
1  0x00007ffff3d2aa69 in KisPaletteModel::index(int, int, QModelIndex
const&) const () from /usr/lib64/libkritawidgets.so.18
2  0x00007ffff5812796 in
QAbstractItemView::setModel(QAbstractItemModel*) () from
/usr/lib64/libQt5Widgets.so.5
3  0x00007ffff582e749 in QHeaderView::setModel(QAbstractItemModel*) ()
from /usr/lib64/libQt5Widgets.so.5
4  0x00007ffff5871493 in QTableView::setModel(QAbstractItemModel*) ()
from /usr/lib64/libQt5Widgets.so.5
5  0x00007ffff3d31e17 in
KisPaletteView::setPaletteModel(KisPaletteModel*) () from
/usr/lib64/libkritawidgets.so.18
6  0x00007ffff3d2691e in
KisDlgInternalColorSelector::KisDlgInternalColorSelector(QWidget*,
KoColor, KisDlgInternalColorSelector::Config, QString const&,
KoColorDisplayRendererInterface const*) () from
/usr/lib64/libkritawidgets.so.18
7  0x00007ffff7000d67 in
KoDualColorButton::Private::init(KoDualColorButton*) () from
/usr/lib64/libkritaui.so.18
8  0x00007ffff7002c5b in KoDualColorButton::KoDualColorButton(KoColor
const&, KoColor const&, KoColorDisplayRendererInterface const*,
QWidget*, QWidget*) ()
  from /usr/lib64/libkritaui.so.18
9  0x00007ffff6e2b5b5 in KisControlFrame::setup(QWidget*) () from
/usr/lib64/libkritaui.so.18
10 0x00007ffff71014ea in KisViewManager::KisViewManager(QWidget*,
KActionCollection*) () from /usr/lib64/libkritaui.so.18
11 0x00007ffff70cb72b in KisMainWindow::KisMainWindow(QUuid) () from
/usr/lib64/libkritaui.so.18
12 0x00007ffff70d8352 in KisPart::createMainWindow(QUuid) () from
/usr/lib64/libkritaui.so.18
13 0x00007ffff70d85de in KisPart::startBlankSession() () from
/usr/lib64/libkritaui.so.18
14 0x00007ffff70995b9 in KisApplication::start(KisApplicationArguments
const&) () from /usr/lib64/libkritaui.so.18
15 0x0000555555e4e229 in main ()

The KisPaletteModel::index() call is inside an Q_ASSERT_X in
QAbstractItemView::setModel(), so you have to compile Qt in debug mode
to reproduce this crash.

m_rowGroupNameMap is empty during the startup.