SUMMARY
Kontact will crash when opening. Choosing "Restart application" mostly works.
See backtrace below.


STEPS TO REPRODUCE
1. Log into Plasma desktop
2. Click on Kontact icon to open the application

OBSERVED RESULT
3. Kde reports a crash and proposes to restart the application
4. Often works. If crashes again, try restart until it works.

EXPECTED RESULT
Application opens...

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 5.26.0
(available in About System)
KDE Plasma Version: 5.26.0
KDE Frameworks Version: 5.99.0
Qt Version: 5.15.6

ADDITIONAL INFORMATION
Running in gdb gave me this:

[...]
Downloading 0.50 MB separate debug info for /usr/lib/x86_64-linux-gnu/qt5/plugins/texttospeech/libqtexttospeech_speechd.so
Downloading 0.05 MB separate debug info for /lib/x86_64-linux-gnu/libspeechd.so.2                            
[New Thread 0x7fff47fff6c0 (LWP 94325)]                                                                      

Thread 1 "kontact" received signal SIGSEGV, Segmentation fault.
__strlen_evex () at ../sysdeps/x86_64/multiarch/strlen-evex.S:79
Download failed: Argument invalide.  Continuing without source file ./string/../sysdeps/x86_64/multiarch/strlen-evex.S.
79      ../sysdeps/x86_64/multiarch/strlen-evex.S: Aucun fichier ou dossier de ce type.
(gdb) backtrace
#0  __strlen_evex () at ../sysdeps/x86_64/multiarch/strlen-evex.S:79
#1  0x00007fff5907abda in get_param_str (reply=reply@entry=0x0, num=num@entry=1, err=err@entry=0x7fffffffc5ec)
    at /build/speech-dispatcher-jyoIDo/speech-dispatcher-0.11.3/src/api/c/libspeechd.c:2003
#2  0x00007fff5907b9a7 in spd_execute_command_with_list_reply (connection=<optimized out>, command=<optimized out>)
    at /build/speech-dispatcher-jyoIDo/speech-dispatcher-0.11.3/src/api/c/libspeechd.c:1541
#3  0x00007fff59087aef in QTextToSpeechEngineSpeechd::connectToSpeechDispatcher (this=this@entry=0x555555eae710)
    at /build/qtspeech-opensource-src-L42tPM/qtspeech-opensource-src-5.15.6/src/plugins/tts/speechdispatcher/qtexttospeech_speechd.cpp:102
#4  0x00007fff59089f5b in QTextToSpeechEngineSpeechd::QTextToSpeechEngineSpeechd (this=0x555555eae710)
    at /build/qtspeech-opensource-src-L42tPM/qtspeech-opensource-src-5.15.6/src/plugins/tts/speechdispatcher/qtexttospeech_speechd.cpp:70
#5  QTextToSpeechPluginSpeechd::createTextToSpeechEngine (this=<optimized out>, parameters=..., parent=<optimized out>, errorString=<optimized out>)
    at /build/qtspeech-opensource-src-L42tPM/qtspeech-opensource-src-5.15.6/src/plugins/tts/speechdispatcher/qtexttospeech_speechd_plugin.cpp:43
#6  0x00007fffe8b6fcae in QTextToSpeechPrivate::QTextToSpeechPrivate (this=<optimized out>, speech=<optimized out>, engine=..., this=<optimized out>, 
    speech=<optimized out>, engine=...) at /build/qtspeech-opensource-src-L42tPM/qtspeech-opensource-src-5.15.6/src/tts/qtexttospeech.cpp:75
#7  0x00007fffe8b70122 in QTextToSpeech::QTextToSpeech (this=<optimized out>, engine=..., parent=<optimized out>, this=<optimized out>, engine=..., 
    parent=<optimized out>) at /build/qtspeech-opensource-src-L42tPM/qtspeech-opensource-src-5.15.6/src/tts/qtexttospeech.cpp:220
#8  0x00007fffec37b9fb in KPIMTextEdit::TextToSpeech::reloadSettings (this=0x7fffec425e60 <KPIMTextEdit::TextToSpeech::self()::s_self>)
    at ./src/texttospeech/texttospeech.cpp:30
#9  0x00007fffec37bb14 in KPIMTextEdit::TextToSpeech::self () at ./src/texttospeech/texttospeech.cpp:48
#10 0x00007fffec37e6e1 in KPIMTextEdit::TextToSpeechInterface::TextToSpeechInterface (this=this@entry=0x555555eaca60, 
    textToSpeechWidget=textToSpeechWidget@entry=0x555555ea4690, parent=parent@entry=0x555555ea4690) at ./src/texttospeech/texttospeechinterface.cpp:27
#11 0x00007fffec37c85b in KPIMTextEdit::TextToSpeechWidget::TextToSpeechWidget (this=0x555555ea4690, parent=<optimized out>)
    at ./src/texttospeech/texttospeechwidget.cpp:82
#12 0x00007fff5a4c68ce in MessageViewer::ViewerPrivate::createWidgets (this=0x555555d60830) at ./messageviewer/src/viewer/viewer_p.cpp:1419
#13 0x00007fff5a4d9354 in MessageViewer::ViewerPrivate::ViewerPrivate (this=this@entry=0x555555d60830, aParent=aParent@entry=0x555555e2b000, 
    mainWindow=mainWindow@entry=0x555555add520, actionCollection=actionCollection@entry=0x5555558f1120) at ./messageviewer/src/viewer/viewer_p.cpp:214
#14 0x00007fff5a4c15d4 in MessageViewer::Viewer::Viewer (this=this@entry=0x555555e2b000, aParent=aParent@entry=0x555555e254d0, 
    mainWindow=mainWindow@entry=0x555555add520, actionCollection=0x5555558f1120) at ./messageviewer/src/viewer/viewer.cpp:67
#15 0x00007fff5ae8c080 in KMReaderWin::KMReaderWin (this=this@entry=0x555555e254d0, aParent=aParent@entry=0x555555add520, 
    mainWindow=mainWindow@entry=0x555555add520, actionCollection=<optimized out>) at ./src/kmreaderwin.cpp:86
#16 0x00007fff5aede89e in KMMainWidget::createWidgets (this=0x555555add520) at ./src/kmmainwidget.cpp:1046
#17 0x00007fff5aedf9ea in KMMainWidget::KMMainWidget (this=this@entry=0x555555add520, parent=parent@entry=0x555555d41350, 
    aGUIClient=aGUIClient@entry=0x555555a571d0, actionCollection=<optimized out>, config=...) at ./src/kmmainwidget.cpp:241
#18 0x00007fff5b0052c7 in KMailPart::KMailPart (this=0x555555a571a0, parentWidget=<optimized out>, parent=<optimized out>, __in_chrg=<optimized out>, 
    __vtt_parm=<optimized out>) at ./src/kmail_part.cpp:69
#19 0x00007fff5b0058b5 in KPluginFactory::createPartInstance<KMailPart> (parentWidget=0x7fffd80064f0, parent=0x7fffd80064f0, args=...)
    at /usr/include/KF5/KCoreAddons/kpluginfactory.h:897
#20 0x00007ffff7db90a3 in KPluginFactory::create(char const*, QWidget*, QObject*, QList<QVariant> const&, QString const&) ()
   from /lib/x86_64-linux-gnu/libKF5CoreAddons.so.5
#21 0x00007ffff7f47abf in KPluginFactory::create<KParts::Part> (args=..., parent=0x7fffd80064f0, this=0x555555a57460)
    at /usr/include/KF5/KCoreAddons/kpluginfactory.h:939
#22 KPluginFactory::instantiatePlugin<KParts::Part> (args=..., parent=0x7fffd80064f0, data=...) at /usr/include/KF5/KCoreAddons/kpluginfactory.h:509
#23 KontactInterface::Core::createPart (this=0x7fffd80064f0, libname=0x5555559ccfe8 "kmailpart") at ./src/core.cpp:69
#24 0x00007ffff7f490d2 in KontactInterface::Plugin::loadPart (this=this@entry=0x555555a01bf0) at ./src/plugin.cpp:125
#25 0x00007fff5b0bbc7a in KMailPlugin::createPart (this=0x555555a01bf0) at ./src/kontactplugin/kmail/kmail_plugin.cpp:149
#26 0x00007ffff7f4b27c in KontactInterface::Plugin::part (this=this@entry=0x555555a01bf0) at ./src/plugin.cpp:136
#27 0x00007ffff7f7898c in Kontact::MainWindow::selectPlugin (this=0x7fffd80064f0, plugin=0x555555a01bf0) at ./src/mainwindow.cpp:587
#28 0x00007ffff7f79f74 in Kontact::MainWindow::loadSettings (this=this@entry=0x7fffd80064f0) at ./src/mainwindow.cpp:716
#29 0x00007ffff7f7e169 in Kontact::MainWindow::initObject (this=0x7fffd80064f0) at ./src/mainwindow.cpp:155
#30 0x00007ffff7f7ebae in Kontact::MainWindow::MainWindow (this=<optimized out>, this=<optimized out>) at ./src/mainwindow.cpp:91
#31 0x000055555555a6f5 in KontactApp::activate (this=0x7fffffffdb00, args=..., workingDir=...) at ./src/main.cpp:116
#32 0x00007ffff7f4c213 in KontactInterface::PimUniqueApplication::start (arguments=...) at ./src/pimuniqueapplication.cpp:143
#33 0x0000555555559642 in main (argc=<optimized out>, argv=<optimized out>) at ./src/main.cpp:198