SegFault on boot latest master on linux

If I run latest commit on my Arch Linux x86-64 Mate machine, I get following in console:

./MuseScoreNightly-201707052208-master-5a79342-x86_64.AppImage 
QApplication: invalid style override passed, ignoring it.
/tmp/.mount_QnsvM0/AppRun: line 18: 32742 Segmentation fault      (core dumped) "${APPDIR}/bin/mscore-portable-nightly" "$@"

The stack trace in qtcreator is:

1 raise                                                                             0x7fffeb131a10 
2 abort                                                                             0x7fffeb13313a 
3 QMessageLogger::fatal(const char *, ...) const                                    0x7fffebad4e21 
4 qt_assert_x(const char *, const char *, const char *, int)                        0x7fffebad0441 
5 QList::operator[]                             qlist.h           548  0xd4041b       
6 Ms::StartupWizard::layoutInput                             startupWizard.cpp 85   0xeceeb4       
7 Ms::MuseScore::MuseScore                                   musescore.cpp     1335 0xc4ca1b       
8 main                                                       musescore.cpp     6172 0xc6fc26       

Happens on the line in StartupWizard::layoutInput():

  QString result = QInputDialog::getItem(new QWidget(), "Startup Wizard", labelMessage, langToLayout->values(lang)[0]);

Apparently can't access index 0 according to the assert failure "QList::operator[]", "index out of range"