kwin crashes with segfault when selecting icon theme

Kubuntu 16.04, kwin-x11 4:5.5.5-0ubuntu1.

I used the System Settings > Icons page to select an icon theme that I downloaded (Snowish-1.3). When I clicked Apply, kwin crashed and was restarted. The icons change did not take effect. See below for the stack trace:

Application: KWin (kwin_x11), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[Current thread is 1 (Thread 0x7fe41687d900 (LWP 20809))]

Thread 4 (Thread 0x7fe3f186e700 (LWP 20820)):
#0 0x00007fe416378d13 in select () at ../sysdeps/unix/syscall-template.S:84
#1 0x00007fe414b7d10f in qt_safe_select (nfds=15, fdread=fdread@entry=0x7fe3e4000a78, fdwrite=fdwrite@entry=0x7fe3e4000d08, fdexcept=fdexcept@entry=0x7fe3e4000f98, orig_timeout=orig_timeout@entry=0x0) at kernel/qcore_unix.cpp:75
#2 0x00007fe414b7ec0e in QEventDispatcherUNIX::select (timeout=0x0, exceptfds=0x7fe3e4000f98, writefds=0x7fe3e4000d08, readfds=0x7fe3e4000a78, nfds=<optimized out>, this=0x7fe3e40008c0) at kernel/qeventdispatcher_unix.cpp:320
#3 QEventDispatcherUNIXPrivate::doSelect (this=this@entry=0x7fe3e40008e0, flags=..., flags@entry=..., timeout=timeout@entry=0x0) at kernel/qeventdispatcher_unix.cpp:196
#4 0x00007fe414b7f13e in QEventDispatcherUNIX::processEvents (this=0x7fe3e40008c0, flags=...) at kernel/qeventdispatcher_unix.cpp:607
#5 0x00007fe414b28dea in QEventLoop::exec (this=this@entry=0x7fe3f186dca0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#6 0x00007fe4149458a4 in QThread::exec (this=this@entry=0x18459c0) at thread/qthread.cpp:503
#7 0x00007fe40f45b3c5 in QQmlThreadPrivate::run (this=0x18459c0) at qml/ftw/qqmlthread.cpp:141
#8 0x00007fe41494a84e in QThreadPrivate::start (arg=0x18459c0) at thread/qthread_unix.cpp:331
#9 0x00007fe4102fe6fa in start_thread (arg=0x7fe3f186e700) at pthread_create.c:333
#10 0x00007fe416382b5d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 3 (Thread 0x7fe3e8bbd700 (LWP 20830)):
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x00007fe413ad2bd4 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Script.so.5
#2 0x00007fe413ad2c19 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Script.so.5
#3 0x00007fe4102fe6fa in start_thread (arg=0x7fe3e8bbd700) at pthread_create.c:333
#4 0x00007fe416382b5d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 2 (Thread 0x7fe3f25e1700 (LWP 21261)):
#0 0x00007fe416378d13 in select () at ../sysdeps/unix/syscall-template.S:84
#1 0x00007fe414b7d10f in qt_safe_select (nfds=14, fdread=fdread@entry=0x7fe3ec013588, fdwrite=fdwrite@entry=0x7fe3ec013818, fdexcept=fdexcept@entry=0x7fe3ec013aa8, orig_timeout=orig_timeout@entry=0x0) at kernel/qcore_unix.cpp:75
#2 0x00007fe414b7ec0e in QEventDispatcherUNIX::select (timeout=0x0, exceptfds=0x7fe3ec013aa8, writefds=0x7fe3ec013818, readfds=0x7fe3ec013588, nfds=<optimized out>, this=0x7fe3ec0008c0) at kernel/qeventdispatcher_unix.cpp:320
#3 QEventDispatcherUNIXPrivate::doSelect (this=this@entry=0x7fe3ec0133f0, flags=..., flags@entry=..., timeout=timeout@entry=0x0) at kernel/qeventdispatcher_unix.cpp:196
#4 0x00007fe414b7f13e in QEventDispatcherUNIX::processEvents (this=0x7fe3ec0008c0, flags=...) at kernel/qeventdispatcher_unix.cpp:607
#5 0x00007fe414b28dea in QEventLoop::exec (this=this@entry=0x7fe3f25e0ca0, flags=..., flags@entry=...) at kernel/qeventloop.cpp:204
#6 0x00007fe4149458a4 in QThread::exec (this=this@entry=0x1ed5e80) at thread/qthread.cpp:503
#7 0x00007fe40f45b3c5 in QQmlThreadPrivate::run (this=0x1ed5e80) at qml/ftw/qqmlthread.cpp:141
#8 0x00007fe41494a84e in QThreadPrivate::start (arg=0x1ed5e80) at thread/qthread_unix.cpp:331
#9 0x00007fe4102fe6fa in start_thread (arg=0x7fe3f25e1700) at pthread_create.c:333
#10 0x00007fe416382b5d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

Thread 1 (Thread 0x7fe41687d900 (LWP 20809)):
[KCrash Handler]
#6 QtPrivate::RefCount::ref (this=0x0) at /usr/include/x86_64-linux-gnu/qt5/QtCore/qrefcount.h:54
#7 QV4::Heap::String::toQString (this=<optimized out>) at jsruntime/qv4string_p.h:84
#8 QV4::String::toQString (this=<optimized out>) at jsruntime/qv4string_p.h:145
#9 QV4::Heap::StringObject::StringObject (this=<optimized out>, engine=0x1d2e940, val=...) at jsruntime/qv4stringobject.cpp:91
#10 0x00007fe40f31b685 in QV4::MemoryManager::alloc<QV4::StringObject, QV4::ExecutionEngine*, QV4::Value> (arg2=..., arg1=0x1d2e940, this=<optimized out>) at jsruntime/qv4mm_p.h:126
#11 QV4::ExecutionEngine::newStringObject (this=0x1d2e940, value=...) at jsruntime/qv4engine.cpp:557
#12 0x00007fe40f3b48b2 in QV4::Runtime::getProperty (engine=0x1d2e940, object=..., nameIndex=<optimized out>) at jsruntime/qv4runtime.cpp:686
#13 0x00007fe3e8bd3a99 in ?? ()
#14 0x00007fe413482b02 in KDecoration2::Decoration::staticMetaObject () from /usr/lib/x86_64-linux-gnu/libkdecorations2.so.5
#15 0x0000000000000029 in ?? ()
#16 0x000000000231ad00 in ?? ()
#17 0x0000000000000001 in ?? ()
#18 0x00007ffc3c4d08d0 in ?? ()
#19 0x00007fe40fa9800a in QQuickRectangle::qt_static_metacall (_o=<optimized out>, _c=<optimized out>, _id=<optimized out>, _a=<optimized out>) at .moc/moc_qquickrectangle_p.cpp:573
#20 0x0000000001d2e940 in ?? ()
#21 0x00007ffc3c4d0930 in ?? ()
#22 0x00000000023282e8 in ?? ()
#23 0x0000000000000003 in ?? ()
#24 0x0000000002325af0 in ?? ()
#25 0x00007fe40f59d2a0 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Qml.so.5
#26 0x00007fe3524bd008 in ?? ()
#27 0x0000000001d2e940 in ?? ()
#28 0x00007fe3ea0fd030 in ?? ()
#29 0x00007fe3e8058a00 in ?? ()
#30 0x0000000000000000 in ?? ()