QGIS 3.18.1 crash on Ubuntu 20.10 changing display of LiDAR point cloud data

[ATL-Flaneur]

Describe the bug

QGIS crashes when attempting to change the rendering of a LiDAR point cloud (LPC) dataset.

How to Reproduce

Load dataset "Serpent Mound.qgz."

Dataset: download.

Select "View" -> "Panels" -> "Layer Styling"

Change "Attribution Classification" to "Attribute By Ramp"

QGIS crashes with the following backtrace:

QGIS died on signal 11[New LWP 1344]
[New LWP 1381]
[New LWP 1382]
[New LWP 1384]
[New LWP 1389]
[New LWP 1390]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
0x00007fb9bd67e68f in __GI___wait4 (pid=1410, stat_loc=0x7ffcff0d572c, options=0, usage=0x0) at ../sysdeps/unix/sysv/linux/wait4.c:30
30	../sysdeps/unix/sysv/linux/wait4.c: No such file or directory.
[Current thread is 1 (Thread 0x7fb9ad9a7080 (LWP 1341))]
#0  0x00007fb9bd67e68f in __GI___wait4 (pid=1410, stat_loc=0x7ffcff0d572c, options=0, usage=0x0) at ../sysdeps/unix/sysv/linux/wait4.c:30
        sc_ret = -512
        sc_cancel_oldtype = 0
        sc_ret = <optimized out>
#1  0x000055bc22ddef54 in ?? ()
No symbol table info available.
#2  <signal handler called>
No locals.
#3  0x00007fb9be67bffb in QgsPointCloudAttributeByRampRenderer::createLegendNodes(QgsLayerTreeLayer*) () from /lib/libqgis_core.so.3.18.1
No symbol table info available.
#4  0x00007fb9be351d5f in QgsDefaultPointCloudLayerLegend::createLayerTreeModelLegendNodes(QgsLayerTreeLayer*) () from /lib/libqgis_core.so.3.18.1
No symbol table info available.
#5  0x00007fb9bdf99772 in QgsLayerTreeModel::addLegendToLayer(QgsLayerTreeLayer*) () from /lib/libqgis_core.so.3.18.1
No symbol table info available.
#6  0x00007fb9bdf9a3d2 in QgsLayerTreeModel::refreshLayerLegend(QgsLayerTreeLayer*) () from /lib/libqgis_core.so.3.18.1
No symbol table info available.
#7  0x00007fb9bf6492e6 in ?? () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#8  0x00007fb9bf6492e6 in ?? () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#9  0x00007fb9bf6492e6 in ?? () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#10 0x00007fb9be683bde in QgsPointCloudLayer::setRenderer(QgsPointCloudRenderer*) () from /lib/libqgis_core.so.3.18.1
No symbol table info available.
#11 0x00007fb9c0f17f77 in QgsPointCloudRendererPropertiesWidget::apply() () from /lib/libqgis_gui.so.3.18.1
No symbol table info available.
#12 0x00007fb9c1ad25b9 in QgsLayerStylingWidget::apply() () from /lib/libqgis_app.so.3.18.1
No symbol table info available.
#13 0x00007fb9bf6492e6 in ?? () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#14 0x00007fb9bf64ce2e in QTimer::timeout(QTimer::QPrivateSignal) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#15 0x00007fb9bf63f58f in QObject::event(QEvent*) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#16 0x00007fb9c00c9013 in QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /lib/x86_64-linux-gnu/libQt5Widgets.so.5
No symbol table info available.
#17 0x00007fb9be231b43 in QgsApplication::notify(QObject*, QEvent*) () from /lib/libqgis_core.so.3.18.1
No symbol table info available.
#18 0x00007fb9bf6131ca in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#19 0x00007fb9bf669b73 in QTimerInfoList::activateTimers() () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#20 0x00007fb9bf66a46c in ?? () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#21 0x00007fb9b567d62b in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#22 0x00007fb9b567d8d8 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#23 0x00007fb9b567d9a3 in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
No symbol table info available.
#24 0x00007fb9bf66a843 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#25 0x00007fb9bf611a4b in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#26 0x00007fb9bf619fc6 in QCoreApplication::exec() () from /lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#27 0x000055bc22ddbee2 in ?? ()
No symbol table info available.
#28 0x00007fb9bd5c8cb2 in __libc_start_main (main=0x55bc22dd93e0, argc=1, argv=0x7ffcff0d7738, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffcff0d7728) at ../csu/libc-start.c:314
        self = <optimized out>
        result = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, 2177349525172677884, 94266527180064, 0, 0, 0, 5383706449149455612, 5349221780590849276}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x1, 0x7ffcff0d7738}, data = {prev = 0x0, cleanup = 0x0, canceltype = 1}}}
        not_first_call = <optimized out>
#29 0x000055bc22dde54e in ?? ()
No symbol table info available.
[Inferior 1 (process 1341) detached]
gdb returned 0
Aborted (core dumped)

QGIS and OS versions

QGIS version: 3.18.1-Zürich
QGIS code revision: 202f1bf7e5
Compiled against Qt: 5.14.2
Running against Qt: 5.14.2
Compiled against GDAL/OGR: 3.1.3
Running against GDAL/OGR: 3.1.3
Compiled against GEOS: 3.8.1-CAPI-1.13.3
Running against GEOS: 3.8.1-CAPI-1.13.3
Compiled against SQLite: 3.33.0
Running against SQLite: 3.33.0
Compiled against PDAL: 2.1.0
Running against PDAL: 2.1.0 (git-version: Release)
PostgreSQL Client Version: 12.6 (Ubuntu 12.6-0ubuntu0.20.10.1)
SpatiaLite Version: 5.0.0
QWT Version: 6.1.4
QScintilla2 Version: 2.11.2
Compiled against PROJ: 7.1.0
Running against PROJ: Rel. 7.1.0, August 1st, 2020
OS Version: Ubuntu 20.10
Active python plugins: db_manager; MetaSearch; processing

Linux version:

$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 20.10
Release:	20.10
Codename:	groovy