SUMMARY

When I use dolphin to navigate in folders containing SUB files, 

STEPS TO REPRODUCE
1. In dolphin activate video files preview
2. Use dolphin to view the folder containing the attached foo.sub file

OBSERVED RESULT

crash

EXPECTED RESULT

no crash

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.14.3
KDE Frameworks Version: 5.51
Qt Version: 5.11.2

ADDITIONAL INFORMATION

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 0x7fa96ba4d780 (LWP 948345))]

Thread 2 (Thread 0x7fa968ecb700 (LWP 948347)):
#0  0x00007fa96f837b99 in __GI___poll (fds=fds@entry=0x7fa968ecad38, nfds=nfds@entry=1, timeout=timeout@entry=-1) at ../sysdeps/unix/sysv/linux/poll.c:29
#1  0x00007fa9703e9cf7 in poll (__timeout=-1, __nfds=1, __fds=0x7fa968ecad38) at /usr/include/x86_64-linux-gnu/bits/poll2.h:46
#2  0x00007fa9703e9cf7 in _xcb_conn_wait (c=c@entry=0x562a84fe9790, cond=cond@entry=0x562a84fe97d0, vector=vector@entry=0x0, count=count@entry=0x0) at ../../src/xcb_conn.c:479
#3  0x00007fa9703eb91a in xcb_wait_for_event (c=0x562a84fe9790) at ../../src/xcb_in.c:697
#4  0x00007fa96a0a3519 in QXcbEventReader::run() (this=0x562a84ff86b0) at qxcbconnection.h:409
#5  0x00007fa96f9ccc97 in QThreadPrivate::start(void*) (arg=0x562a84ff86b0) at thread/qthread_unix.cpp:367
#6  0x00007fa96e89dfa3 in start_thread (arg=<optimized out>) at pthread_create.c:486
#7  0x00007fa96f84284f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Thread 1 (Thread 0x7fa96ba4d780 (LWP 948345)):
[KCrash Handler]
#6  0x00007fa96b7814f4 in ffmpegthumbnailer::MovieDecoder::seek(int) (this=this@entry=0x7ffe06f5b520, timeInSeconds=<optimized out>) at ./ffmpegthumbnailer/moviedecoder.cpp:202
#7  0x00007fa96b78320a in ffmpegthumbnailer::VideoThumbnailer::generateThumbnail(QString const&, ffmpegthumbnailer::ImageWriter&, QImage&) (this=this@entry=0x562a8509f5f8, videoFile=..., imageWriter=..., image=...) at ./ffmpegthumbnailer/videothumbnailer.cpp:105
#8  0x00007fa96b783359 in ffmpegthumbnailer::VideoThumbnailer::generateThumbnail(QString const&, QImage&) (this=this@entry=0x562a8509f5f8, videoFile=..., image=...) at ./ffmpegthumbnailer/videothumbnailer.cpp:141
#9  0x00007fa96b780793 in FFMpegThumbnailer::create(QString const&, int, int, QImage&) (this=0x562a8509f5e0, path=..., width=<optimized out>, img=...) at ./ffmpegthumbnailer.cpp:46
#10 0x00007fa9705d39fe in  () at /usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/thumbnail.so
#11 0x00007fa96b3ecdf6 in KIO::SlaveBase::dispatch(int, QByteArray const&) () at /lib/x86_64-linux-gnu/libKF5KIOCore.so.5
#12 0x00007fa96b3e8196 in KIO::SlaveBase::dispatchLoop() () at /lib/x86_64-linux-gnu/libKF5KIOCore.so.5
#13 0x00007fa9705d108d in kdemain () at /usr/lib/x86_64-linux-gnu/qt5/plugins/kf5/kio/thumbnail.so
#14 0x0000562a84cb6e1c in  ()
#15 0x0000562a84cb7eea in  ()
#16 0x0000562a84cb88fb in  ()
#17 0x0000562a84cb3645 in  ()
#18 0x00007fa96f76d09b in __libc_start_main (main=0x562a84cb2c70, argc=2, argv=0x7ffe06f5c0a8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7ffe06f5c098) at ../csu/libc-start.c:308
#19 0x0000562a84cb42ca in _start ()
[Inferior 1 (process 948345) detached]