PCMANFM crashes on opening a directory with a large number of images

[Volodya]

To reproduce:
create a directory with 10k+ images
open that directory by double clicking the icon
sometimes this will crash pcmanfm

Note:
if you open a directory in a new tab, that does not freeze pcmanfm and it will crash much less frequiently

Note:
if new image files are being created in that directory as you are opening it, that will increase the chance of a crash

Note:
if imediately after crash you will try to open the same directory again, it will almost never crash

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: pcmanfm 1.2.5-3ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-112.113-generic 4.15.18
Uname: Linux 4.15.0-112-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.15
Architecture: amd64
Config_pcmanfm_System_xubuntu: Error: [Errno 2] No such file or directory: '/etc/xdg/pcmanfm/xubuntu/pcmanfm.conf'
CurrentDesktop: XFCE
Date: Tue Aug 4 06:12:54 2020
InstallationDate: Installed on 2018-11-24 (618 days ago)
InstallationMedia: Xubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
SourcePackage: pcmanfm
Udisks_dump: Error: [Errno 2] No such file or directory: 'udisks': 'udisks'
UpgradeStatus: No upgrade log present (probably fresh install)

[Volodya (volodya)]

$ pcmanfm
** Message: 06:19:48.335: x-terminal-emulator has very limited support, consider choose another terminal
  match profile: profile-zero

(pcmanfm:6298): GLib-CRITICAL **: 06:19:48.599: g_file_test: assertion 'filename != NULL' failed
  match profile: thumbnail_directory
  match profile: profile-zero

(pcmanfm:6298): GLib-CRITICAL **: 06:21:39.337: g_file_test: assertion 'filename != NULL' failed
  match profile: thumbnail_directory
  match profile: profile-zero

(pcmanfm:6298): GLib-CRITICAL **: 06:21:47.542: g_file_test: assertion 'filename != NULL' failed
  match profile: thumbnail_directory
  match profile: profile-zero

(pcmanfm:6298): GLib-CRITICAL **: 06:22:08.378: g_file_test: assertion 'filename != NULL' failed
  match profile: thumbnail_directory
  match profile: profile-zero

(pcmanfm:6298): GLib-CRITICAL **: 06:26:56.341: g_file_test: assertion 'filename != NULL' failed
  match profile: thumbnail_directory
Segmentation fault (core dumped)

[Volodya (volodya)]

$ gdb pcmanfm
GNU gdb (Ubuntu 8.1-0ubuntu3.2) 8.1.0.20180409-git
Copyright (C) 2018 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law. Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from pcmanfm...(no debugging symbols found)...done.
(gdb) run
Starting program: /usr/bin/pcmanfm
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffee41c700 (LWP 16011)]
[New Thread 0x7fffedc1b700 (LWP 16012)]
** Message: 06:28:25.814: x-terminal-emulator has very limited support, consider choose another terminal
[New Thread 0x7fffed41a700 (LWP 16013)]
[New Thread 0x7fffecc19700 (LWP 16014)]
[New Thread 0x7fffd7de2700 (LWP 16016)]
  match profile: profile-zero

(pcmanfm:16007): GLib-CRITICAL **: 06:28:26.184: g_file_test: assertion 'filename != NULL' failed
  match profile: thumbnail_directory
[Thread 0x7fffecc19700 (LWP 16014) exited]
[New Thread 0x7fffecc19700 (LWP 16017)]
[Thread 0x7fffecc19700 (LWP 16017) exited]
[New Thread 0x7fffecc19700 (LWP 16018)]
[Thread 0x7fffecc19700 (LWP 16018) exited]
[New Thread 0x7fffd73db700 (LWP 16019)]
[Thread 0x7fffd73db700 (LWP 16019) exited]
[Thread 0x7fffd7de2700 (LWP 16016) exited]
[New Thread 0x7fffd7de2700 (LWP 16217)]
[New Thread 0x7fffd73db700 (LWP 16219)]
[Thread 0x7fffd7de2700 (LWP 16217) exited]
[Thread 0x7fffd73db700 (LWP 16219) exited]
[Thread 0x7fffed41a700 (LWP 16013) exited]
[New Thread 0x7fffed41a700 (LWP 16429)]
[New Thread 0x7fffd73db700 (LWP 16431)]
[Thread 0x7fffd73db700 (LWP 16431) exited]
[New Thread 0x7fffd73db700 (LWP 16432)]

Thread 1 "pcmanfm" received signal SIGSEGV, Segmentation fault.
0x00007ffff6150170 in fm_file_info_get_path () from /usr/lib/x86_64-linux-gnu/libfm.so.4
(gdb) bt
#0 0x00007ffff6150170 in fm_file_info_get_path () at /usr/lib/x86_64-linux-gnu/libfm.so.4
#1 0x00007ffff6152abf in () at /usr/lib/x86_64-linux-gnu/libfm.so.4
#2 0x00007ffff5b5810d in g_closure_invoke () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#3 0x00007ffff5b6b05e in () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#4 0x00007ffff5b73715 in g_signal_emit_valist () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#5 0x00007ffff5b7412f in g_signal_emit () at /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#6 0x00007ffff6164230 in () at /usr/lib/x86_64-linux-gnu/libfm.so.4
#7 0x00007ffff587d285 in g_main_context_dispatch () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#8 0x00007ffff587d650 in () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#9 0x00007ffff587d962 in g_main_loop_run () at /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0
#10 0x...