SUMMARY
After boot, Baloo crashes every so often. I've got an idea of what may cause this, specifically files with invalid names. The reason for this is that some tools like Gradle output jars which, if certain unicode characters are used, split some of these characters in two. This results in filenames such as "sɹÇ_Æ_É_llá´_Î_-1.0.jar" and similar, possibly containing hidden or invalid characters.

STEPS TO REPRODUCE
Unknown, but here's my suggestion:
1. Create a blank file and rename it to sɹÇ_Æ_É_llá´_Î_-1.0.jar
2. Reboot, as this issue did not happen to me until I rebooted.

OBSERVED RESULT
Baloo crashes

EXPECTED RESULT
Baloo does not crash

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux x86-64 (kernel: 5.8.14-arch1-1)
KDE Plasma Version: 5.20.0
KDE Frameworks Version: 5.75.0
Qt Version: 5.15.1

ADDITIONAL INFORMATION

Crash log:
Application: baloo_file_extractor (baloo_file_extractor), signal: Aborted

[New LWP 4095]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
0x00007f315262f46f in poll () from /usr/lib/libc.so.6
[Current thread is 1 (Thread 0x7f314ef66280 (LWP 4093))]

Thread 2 (Thread 0x7f314e17f640 (LWP 4095)):
#0  0x00007f315262f46f in poll () from /usr/lib/libc.so.6
#1  0x00007f31516035af in ?? () from /usr/lib/libglib-2.0.so.0
#2  0x00007f31515ae131 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#3  0x00007f3152bec95c in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#4  0x00007f3152b9265c in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#5  0x00007f31529acca2 in QThread::exec() () from /usr/lib/libQt5Core.so.5
#6  0x00007f3153516098 in ?? () from /usr/lib/libQt5DBus.so.5
#7  0x00007f31529ade8f in ?? () from /usr/lib/libQt5Core.so.5
#8  0x00007f3151fde3e9 in start_thread () from /usr/lib/libpthread.so.0
#9  0x00007f315263a293 in clone () from /usr/lib/libc.so.6

Thread 1 (Thread 0x7f314ef66280 (LWP 4093)):
[KCrash Handler]
#4  0x00007f3152577615 in raise () from /usr/lib/libc.so.6
#5  0x00007f3152560862 in abort () from /usr/lib/libc.so.6
#6  0x00007f315219f624 in ?? () from /usr/lib/liblmdb.so
#7  0x00007f3152193185 in ?? () from /usr/lib/liblmdb.so
#8  0x00007f3152195716 in ?? () from /usr/lib/liblmdb.so
#9  0x00007f3152195963 in ?? () from /usr/lib/liblmdb.so
#10 0x00007f315219755c in ?? () from /usr/lib/liblmdb.so
#11 0x00007f315219a82e in mdb_cursor_put () from /usr/lib/liblmdb.so
#12 0x00007f315219d64b in mdb_put () from /usr/lib/liblmdb.so
#13 0x00007f31535ac481 in Baloo::DocumentDataDB::put(unsigned long long, QByteArray const&) () from /usr/lib/libKF5BalooEngine.so.5
#14 0x00007f31535c39cf in Baloo::WriteTransaction::replaceDocument(Baloo::Document const&, QFlags<Baloo::DocumentOperation>) () from /usr/lib/libKF5BalooEngine.so.5
#15 0x000056357c71e9f6 in ?? ()
#16 0x000056357c71f591 in ?? ()
#17 0x00007f3152bc07e2 in QObject::event(QEvent*) () from /usr/lib/libQt5Core.so.5
#18 0x00007f3152b93cda in QCoreApplication::notifyInternal2(QObject*, QEvent*) () from /usr/lib/libQt5Core.so.5
#19 0x00007f3152b967d3 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from /usr/lib/libQt5Core.so.5
#20 0x00007f3152bed304 in ?? () from /usr/lib/libQt5Core.so.5
#21 0x00007f31515af924 in g_main_context_dispatch () from /usr/lib/libglib-2.0.so.0
#22 0x00007f3151603621 in ?? () from /usr/lib/libglib-2.0.so.0
#23 0x00007f31515ae131 in g_main_context_iteration () from /usr/lib/libglib-2.0.so.0
#24 0x00007f3152bec941 in QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#25 0x00007f3152b9265c in QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /usr/lib/libQt5Core.so.5
#26 0x00007f3152b9aaf4 in QCoreApplication::exec() () from /usr/lib/libQt5Core.so.5
#27 0x000056357c71d165 in ?? ()
#28 0x00007f3152562152 in __libc_start_main () from /usr/lib/libc.so.6
#29 0x000056357c71d28e in ?? ()
[Inferior 1 (process 4093) detached]