Could be that it is already fixed upstream:
https://cgit.kde.org/kio-extras.git/commit/?id=aaa1edbb74c4fb01affbde7b79bb45d3a9b61f83
Also got a slightly different crash:
Application: kdeinit5 (kdeinit5), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7f9cf416d780 (LWP 6414))]
Thread 3 (Thread 0x7f9cefb91700 (LWP 23487)):
#0 0x00007f9cf7d7eb39 in __GI___poll (fds=fds@entry=0x7f9cefb90e80,
nfds=nfds@entry=2, timeout=timeout@entry=-1) at
../sysdeps/unix/sysv/linux/poll.c:29
#1 0x00007f9cf0415fbf in poll (__timeout=-1, __nfds=2,
__fds=0x7f9cefb90e80) at /usr/include/x86_64-linux-gnu/bits/poll2.h:46
#2 linux_udev_event_thread_main (arg=<optimized out>) at
../../libusb/os/linux_udev.c:192
#3 0x00007f9cf6de2fa3 in start_thread (arg=<optimized out>) at
pthread_create.c:486
#4 0x00007f9cf7d897ef in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:95
Thread 2 (Thread 0x7f9cf0392700 (LWP 6415)):
#0 0x00007f9cf7d7eb39 in __GI___poll (fds=0x7f9ce8003ce0, nfds=1,
timeout=-1) at ../sysdeps/unix/sysv/linux/poll.c:29
#1 0x00007f9cf6242016 in g_main_context_poll (priority=<optimized out>,
n_fds=1, fds=0x7f9ce8003ce0, timeout=<optimized out>,
context=0x7f9ce8000bf0) at ../../../glib/gmain.c:4221
#2 g_main_context_iterate (context=context@entry=0x7f9ce8000bf0,
block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at
../../../glib/gmain.c:3915
#3 0x00007f9cf624213c in g_main_context_iteration
(context=0x7f9ce8000bf0, may_block=may_block@entry=1) at
../../../glib/gmain.c:3981
#4 0x00007f9cf810e16b in QEventDispatcherGlib::processEvents
(this=0x7f9ce8000b20, flags=...) at kernel/qeventdispatcher_glib.cpp:424
#5 0x00007f9cf80bb14b in QEventLoop::exec
(this=this@entry=0x7f9cf0391df0, flags=..., flags@entry=...) at
../../include/QtCore/../../src/corelib/global/qflags.h:140
#6 0x00007f9cf7f0a106 in QThread::exec (this=this@entry=0x7f9cf378cd60
<(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at
../../include/QtCore/../../src/corelib/global/qflags.h:120
#7 0x00007f9cf3712545 in QDBusConnectionManager::run
(this=0x7f9cf378cd60 <(anonymous
namespace)::Q_QGS__q_manager::innerFunction()::holder>) at
qdbusconnection.cpp:178
#8 0x00007f9cf7f13cd7 in QThreadPrivate::start (arg=0x7f9cf378cd60
<(anonymous namespace)::Q_QGS__q_manager::innerFunction()::holder>) at
thread/qthread_unix.cpp:367
#9 0x00007f9cf6de2fa3 in start_thread (arg=<optimized out>) at
pthread_create.c:486
#10 0x00007f9cf7d897ef in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:95
Thread 1 (Thread 0x7f9cf416d780 (LWP 6414)):
[KCrash Handler]
#6 QString::QString (other=..., this=this@entry=0x7fffac2173f8) at
/usr/include/x86_64-linux-gnu/qt5/QtCore/qstring.h:952
#7 CachedDevice::getName (this=0x0) at ./mtp/devicecache.cpp:76
#8 0x00007f9cf3cd8fad in MTPSlave::checkUrl
(this=this@entry=0x7fffac217660, url=..., redirect=redirect@entry=true)
at ./mtp/kio_mtp.cpp:219
#9 0x00007f9cf3cdd2e9 in MTPSlave::fileSystemFreeSpace
(this=0x7fffac217660, url=...) at ./mtp/kio_mtp.cpp:923
#10 0x00007f9cf3d9039f in KIO::SlaveBase::dispatch(int, QByteArray
const&) () from /usr/lib/x86_64-linux-gnu/libKF5KIOCore.so.5
#11 0x00007f9cf3d90876 in KIO::SlaveBase::dispatchLoop() () from
/usr/lib/x86_64-linux-gnu/libKF5KIOCore.so.5
#12 0x00007f9cf3cde7fd in kdemain (argc=<optimized out>, argv=<optimized
out>) at ./mtp/kio_mtp.cpp:56
#13 0x000056345f761e1c in ?? ()
#14 0x000056345f762eea in ?? ()
#15 0x000056345f7638fb in ?? ()
#16 0x000056345f75e645 in ?? ()
#17 0x00007f9cf7cb409b in __libc_start_main (main=0x56345f75dc70,
argc=5, argv=0x7fffac217e48, init=<optimized out>, fini=<optimized out>,
rtld_fini=<optimized out>, stack_end=0x7fffac217e38) at
../csu/libc-start.c:308
#18 0x000056345f75f2ca in ?? ()
[Inferior 1 (process 6414) detached]
