segfault when running org.freedesktop.Platform/x86_64/19.08

[mat8913]

To reproduce:

1. Run flatpak run org.freedesktop.Platform/x86_64/19.08 in separate terminal window/tab
2. In your main terminal, run systemctl --user restart xdg-desktop-portal.service
3. Get this error

   Dec 24 17:46:42 gallium systemd[1298]: Starting Portal service...
   Dec 24 17:46:42 gallium .xdg-desktop-po[30884]: Failed connect to PipeWire: Couldn't connect PipeWire remote
   Dec 24 17:46:43 gallium systemd[1298]: xdg-desktop-portal.service: Main process exited, code=killed, status=11/SEGV
   Dec 24 17:46:43 gallium systemd[1298]: xdg-desktop-portal.service: Failed with result 'signal'.
   Dec 24 17:46:43 gallium systemd[1298]: Failed to start Portal service.
   Dec 24 17:46:43 gallium systemd-coredump[30892]: Process 30884 (.xdg-desktop-po) of user 1000 dumped core.
   

Here's my gdb transcript:

(gdb) run
Starting program: /nix/store/whnnn9rajnmrpddh0nv5v1zjiv3ha74n-xdg-desktop-portal-1.4.2/libexec/.xdg-desktop-portal-wrapped 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/nix/store/xhpwab5kavygbr1fswawmdyqvmn3wa4i-glibc-2.27/lib/libthread_db.so.1".
[New Thread 0x7fffecd08700 (LWP 28793)]
[New Thread 0x7fffe7fff700 (LWP 28794)]
[New Thread 0x7fffe77fe700 (LWP 28795)]
[New Thread 0x7fffe6ffd700 (LWP 28796)]
[New Thread 0x7fffe66dd700 (LWP 28797)]
[Thread 0x7fffe66dd700 (LWP 28797) exited]

** (/nix/store/whnnn9rajnmrpddh0nv5v1zjiv3ha74n-xdg-desktop-portal-1.4.2/libexec/.xdg-desktop-portal-wrapped:28787): WARNING **: 17:30:26.453: Failed connect to PipeWire: Couldn't connect PipeWire remote
[New Thread 0x7fffe66dd700 (LWP 28798)]

Thread 7 ".xdg-desktop-po" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffe66dd700 (LWP 28798)]
0x00007ffff7acbe30 in g_str_hash () from /nix/store/3y35pzzm1fqjxj4gp9pwya9z01d2kdd7-glib-2.62.3/lib/libglib-2.0.so.0
(gdb) backtrace 
#0  0x00007ffff7acbe30 in g_str_hash () from /nix/store/3y35pzzm1fqjxj4gp9pwya9z01d2kdd7-glib-2.62.3/lib/libglib-2.0.so.0
#1  0x00007ffff7acaeef in g_hash_table_lookup () from /nix/store/3y35pzzm1fqjxj4gp9pwya9z01d2kdd7-glib-2.62.3/lib/libglib-2.0.so.0
#2  0x000000000041da66 in get_one_app_state (app_id=app_id@entry=0x0, app_states=app_states@entry=0x5e9e40) at src/background.c:483
#3  0x000000000041e18c in check_background_apps () at src/background.c:720
#4  0x000000000041e3d8 in background_monitor (data=<optimized out>) at src/background.c:803
#5  0x00007ffff7b060fd in g_thread_proxy () from /nix/store/3y35pzzm1fqjxj4gp9pwya9z01d2kdd7-glib-2.62.3/lib/libglib-2.0.so.0
#6  0x00007ffff7a70ef7 in start_thread () from /nix/store/n5xvawbb855dihh8a4l4an06rmz3awb8-glibc-2.27/lib/libpthread.so.0
#7  0x00007ffff79a622f in clone () from /nix/store/n5xvawbb855dihh8a4l4an06rmz3awb8-glibc-2.27/lib/libc.so.6
(gdb) frame 2
#2  0x000000000041da66 in get_one_app_state (app_id=app_id@entry=0x0, app_states=app_states@entry=0x5e9e40) at src/background.c:483
483	  return (AppState)GPOINTER_TO_INT (g_hash_table_lookup (app_states, app_id));
(gdb) print app_states
$1 = (GHashTable *) 0x5e9e40
(gdb) print app_id
$2 = 0x0
(gdb) frame 3
#3  0x000000000041e18c in check_background_apps () at src/background.c:720
720	      idata->state = get_one_app_state (app_id, app_states);
(gdb) print app_id
$3 = 0x0
(gdb) print instance
$4 = (FlatpakInstance *) 0x7fffd0014170
(gdb) print i
$5 = 3
(gdb) print id
$6 = 0x7fffd0019980 "2712149621"
(gdb) print child_pid
$7 = 27962

Process id 27962 corresponds to the bwrap instance for the sandbox spawned in step 1.