xfdesktop crashes at xfdesktop_migrate_backdrop_settings

👋 Hi,

I am testing xfdesktop HEAD (56ddbe79) on a NixOS custom branch with an absolutely fresh VM, xfdesktop crashes for me on startup with the following:

#0  0x00007fe310cec410 in g_hash_table_iter_next (iter=iter@entry=0x7ffdbbbd71b0, 
    key=key@entry=0x7ffdbbbd7178, value=value@entry=0x7ffdbbbd7180) at ../glib/ghash.c:1125
#1  0x0000000000466e44 in xfdesktop_migrate_backdrop_settings (display=0x24e51e50, 
    channel=0x24e2df00) at xfdesktop-common.c:648
#2  0x0000000000429a24 in xfdesktop_application_start (app=app@entry=0x24e224d0)
    at xfdesktop-application.c:1062
#3  0x0000000000429e54 in wait_for_wm_complete (status=<optimized out>, data=0x24e224d0)
    at xfdesktop-application.c:686
#4  wait_for_wm_complete (status=<optimized out>, data=0x24e224d0) at xfdesktop-application.c:671
#5  0x000000000042f927 in cb_wait_for_wm_timeout_destroyed (data=0x24f71010) at xfdesktop-x11.c:383
#6  0x00007fe310cfd4b9 in g_source_callback_unref (cb_data=0x24f7a8b0) at ../glib/gmain.c:1622
#7  g_source_callback_unref (cb_data=0x24f7a8b0) at ../glib/gmain.c:1615
#8  0x00007fe310cfdddf in g_source_destroy_internal (source=source@entry=0x24f7b060, 
    context=context@entry=0x24e30120, have_lock=have_lock@entry=1) at ../glib/gmain.c:1287
#9  0x00007fe310cfdfec in g_main_dispatch (context=context@entry=0x24e30120)
    at ../glib/gmain.c:3374
#10 0x00007fe310d012c7 in g_main_context_dispatch_unlocked (context=0x24e30120)
    at ../glib/gmain.c:4152
#11 g_main_context_iterate_unlocked (context=context@entry=0x24e30120, block=block@entry=1, 
    dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4217
#12 0x00007fe310d018ec in g_main_context_iteration (context=context@entry=0x24e30120, 
    may_block=may_block@entry=1) at ../glib/gmain.c:4282
#13 0x00007fe310f4a6fd in g_application_run (application=application@entry=0x24e224d0, 
    argc=argc@entry=1, argv=argv@entry=0x7ffdbbbd7568) at ../gio/gapplication.c:2712
#14 0x0000000000424312 in main (argc=1, argv=0x7ffdbbbd7568) at main.c:64

I also see g_hash_table_iter_init: assertion 'hash_table != NULL' failed in the journal, I wonder if some null checks are missing here? 😂