`simple3d.py` example segfaulted with python3.8

Pyside sample script for `Qt3DCore` segfault in `ShaderBuilder`

`gdb --args python examples/3d/simple3d.py`

```
GNU gdb (GDB) 8.3.1
Copyright (C) 2019 Free Software Foundation, Inc.                                                                       
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
   <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from python...
(No debugging symbols found in python)
(gdb) r
Starting program: /usr/bin/python examples/3d/simple3d.py
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
/usr/lib/../share/gcc-9.2.0/python/libstdcxx/v6/xmethods.py:731: SyntaxWarning: list indices must be integers or slices
, not str; perhaps you missed a comma?
 refcounts = ['_M_refcount']['_M_pi']
[New Thread 0x7ffff07ae700 (LWP 1590206)]
[New Thread 0x7fffee471700 (LWP 1590208)]
[New Thread 0x7fffedc4e700 (LWP 1590209)]
[New Thread 0x7fffed42a700 (LWP 1590210)]
[New Thread 0x7fffecc29700 (LWP 1590211)]
[New Thread 0x7fffd4f71700 (LWP 1590212)]
[New Thread 0x7fffcffff700 (LWP 1590213)]
[New Thread 0x7fffc77fe700 (LWP 1590214)]
[New Thread 0x7fffcf7fe700 (LWP 1590215)]
[New Thread 0x7fffceffd700 (LWP 1590216)]
[New Thread 0x7fffce7fc700 (LWP 1590217)]
[New Thread 0x7fffcdffb700 (LWP 1590218)]
[New Thread 0x7fffcd7fa700 (LWP 1590219)]
[New Thread 0x7fffccff9700 (LWP 1590220)]

Thread 1 "python" received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) bt
#0  0x0000000000000000 in  ()
#1  0x00007ffff19cfff1 in Qt3DRender::Render::ShaderBuilder::syncFromFrontEnd(Qt3DCore::QNode const*, bool) ()
   at /usr/lib/libQt53DRender.so.5
#2  0x00007ffff1cf0570 in Qt3DCore::QAbstractAspectPrivate::createBackendNode(Qt3DCore::NodeTreeChange const&) const
   () at /usr/lib/libQt53DCore.so.5
#3  0x00007ffff1cf06e0 in Qt3DCore::QAbstractAspectPrivate::setRootAndCreateNodes(Qt3DCore::QEntity*, QVector<Qt3DCore:
:NodeTreeChange> const&) () at /usr/lib/libQt53DCore.so.5
#4  0x00007ffff1cf7008 in Qt3DCore::QAspectManager::setRootEntity(Qt3DCore::QEntity*, QVector<Qt3DCore::QNode*> const&)
() at /usr/lib/libQt53DCore.so.5
#5  0x00007ffff1cf3141 in Qt3DCore::QAspectEngine::setRootEntity(QSharedPointer<Qt3DCore::QEntity>) ()
   at /usr/lib/libQt53DCore.so.5
#6  0x00007ffff1ba9e9c in Qt3DExtras::Qt3DWindow::showEvent(QShowEvent*) () at /usr/lib/libQt53DExtras.so.5
#7  0x00007ffff1c72615 in  () at /usr/lib/python3.8/site-packages/PySide2/Qt3DExtras.cpython-38-x86_64-linux-gnu.so
#8  0x00007ffff25349dd in QWindow::event(QEvent*) () at /usr/lib/libQt5Gui.so.5
#9  0x00007ffff1c701a5 in  () at /usr/lib/python3.8/site-packages/PySide2/Qt3DExtras.cpython-38-x86_64-linux-gnu.so
#10 0x00007ffff2c60b88 in  () at /usr/lib/python3.8/site-packages/PySide2/QtGui.cpython-38-x86_64-linux-gnu.so
#11 0x00007ffff638d962 in QCoreApplication::notifyInternal2(QObject*, QEvent*) () at /usr/lib/libQt5Core.so.5
#12 0x00007ffff2534621 in QWindowPrivate::setVisible(bool) () at /usr/lib/libQt5Gui.so.5
#13 0x00007ffff2e77fea in  () at /usr/lib/python3.8/site-packages/PySide2/QtGui.cpython-38-x86_64-linux-gnu.so
#14 0x00007ffff7af0d39 in  () at /usr/lib/libpython3.8.so.1.0
#15 0x00007ffff7ba73c8 in _PyEval_EvalFrameDefault () at /usr/lib/libpython3.8.so.1.0
#16 0x00007ffff7b8fe3b in _PyEval_EvalCodeWithName () at /usr/lib/libpython3.8.so.1.0
#17 0x00007ffff7c193d3 in PyEval_EvalCode () at /usr/lib/libpython3.8.so.1.0
#18 0x00007ffff7c19428 in  () at /usr/lib/libpython3.8.so.1.0
#19 0x00007ffff7c1d623 in  () at /usr/lib/libpython3.8.so.1.0
#20 0x00007ffff7ab83e7 in PyRun_FileExFlags () at /usr/lib/libpython3.8.so.1.0
#21 0x00007ffff7ac2f4a in PyRun_SimpleFileExFlags () at /usr/lib/libpython3.8.so.1.0
#22 0x00007ffff7c2a8be in Py_RunMain () at /usr/lib/libpython3.8.so.1.0
#23 0x00007ffff7c2a9a9 in Py_BytesMain () at /usr/lib/libpython3.8.so.1.0
#24 0x00007ffff7d9a153 in __libc_start_main () at /usr/lib/libc.so.6
#25 0x000055555555505e in _start ()
(gdb)

```