sddm crashed with SIGABRT in qt_message_fatal()

[Olivier Hallot]

Cannot open a VT2, sddm crashes

root@olivier-ntbk:/var/crash# lsb_release -rd
Description: Ubuntu 18.04.1 LTS
Release: 18.04

root@olivier-ntbk:/var/crash# apt-cache policy sddm
sddm:
  Instalado: 0.17.0-1ubuntu7
  Candidato: 0.17.0-1ubuntu7
  Tabela de versão:
 *** 0.17.0-1ubuntu7 500
        500 http://br.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages
        100 /var/lib/dpkg/status

Expected results: open a new session with different user in VT2, keep VT1 with current user, switch between VT1 and VT2 with Ctrl+alt+F1 and Ctrl+Alt+F2.
Actually cannot open more than one user, it should let me open VT2, Vt3... VTn.

What happened instead: sddm crashes, Xorg restart on VT1, previous session is killed, all unsaved data is lost.

ProblemType: Crash
DistroRelease: Ubuntu 18.04
Package: sddm 0.17.0-1ubuntu7
ProcVersionSignature: Ubuntu 4.15.0-38.41-generic 4.15.18
Uname: Linux 4.15.0-38-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.4
Architecture: amd64
CrashCounter: 1
Date: Mon Nov 12 15:06:27 2018
ExecutablePath: /usr/bin/sddm
ExecutableTimestamp: 1524229926
InstallationDate: Installed on 2018-05-10 (185 days ago)
InstallationMedia: Kubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
ProcCmdline: /usr/bin/sddm
ProcCwd: /
ProcEnviron:
 LANG=pt_BR.UTF-8
 LANGUAGE=pt_BR:pt:en
 PATH=(custom, no user)
Signal: 6
SourcePackage: sddm
StacktraceTop:
 QMessageLogger::fatal(char const*, ...) const () from /usr/lib/x86_64-linux-gnu/libQt5Core.so.5
 SDDM::Display::start() ()
 SDDM::Seat::createDisplay(int) ()
 ?? ()
 SeatAdaptor::qt_metacall(QMetaObject::Call, int, void**) ()
Title: sddm crashed with SIGABRT in QMessageLogger::fatal()
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups:

[Apport retracing service (apport)]

StacktraceTop:
 qt_message_fatal (context=..., message=<synthetic pointer>...) at global/qlogging.cpp:1690
 QMessageLogger::fatal (this=this@entry=0x7ffe8f77b4c0, msg=msg@entry=0x55d5aacdcdf0 "Display server failed to start. Exiting") at global/qlogging.cpp:796
 SDDM::Display::start (this=this@entry=0x55d5ab686620) at ./src/daemon/Display.cpp:112
 SDDM::Seat::createDisplay (this=0x55d5ab6815b0, terminalId=2) at ./src/daemon/Seat.cpp:81
 SeatAdaptor::qt_static_metacall (_o=<optimized out>, _c=<optimized out>, _id=<optimized out>, _a=<optimized out>) at ./obj-x86_64-linux-gnu/src/daemon/seatadaptor.moc:116