rare failure in gdbus-peer test: invalid uninstantiatable type '(null)' in cast to 'GDBusServer'

Submitted by Simon McVittie

Description

Thread 1 (Thread 0x7fe93db8b700 (LWP 15920)):
#0  _g_log_abort (breakpoint=breakpoint@entry=1) at /home/smcv/src/glib/glib/gmessages.c:583
#1  0x00007fe941d34e92 in g_logv (log_domain=0x7fe94264b903 "GLib-GObject", log_level=G_LOG_LEVEL_WARNING, format=<optimized out>, args=args@entry=0x7fe93db8a6c8) at /home/smcv/src/glib/glib/gmessages.c:1391
#2  0x00007fe941d3507e in g_log (log_domain=log_domain@entry=0x7fe94264b903 "GLib-GObject", log_level=log_level@entry=G_LOG_LEVEL_WARNING, format=format@entry=0x7fe942653d88 "invalid uninstantiatable type '%s' in cast to '%s'") at /home/smcv/src/glib/glib/gmessages.c:1432
#3  0x00007fe9426443f9 in g_type_check_instance_cast (type_instance=type_instance@entry=0x5623c76c8810, iface_type=<optimized out>) at /home/smcv/src/glib/gobject/gtype.c:4069
#4  0x00007fe94294991a in on_run (service=<optimized out>, socket_connection=0x5623c76c89e0, source_object=<optimized out>, user_data=0x5623c76c8810) at /home/smcv/src/glib/gio/gdbusserver.c:950
#5  0x00007fe942407fce in ffi_call_unix64 () from /usr/lib/x86_64-linux-gnu/libffi.so.6
#6  0x00007fe94240793f in ffi_call () from /usr/lib/x86_64-linux-gnu/libffi.so.6
#7  0x00007fe94261d789 in g_cclosure_marshal_generic_va (closure=0x5623c76ec790, return_value=0x7fe93db8abd0, instance=<optimized out>, args_list=<optimized out>, marshal_data=<optimized out>, n_params=2, param_types=0x5623c76ca940) at /home/smcv/src/glib/gobject/gclosure.c:1604
#8  0x00007fe94261cc3c in _g_closure_invoke_va (closure=closure@entry=0x5623c76ec790, return_value=return_value@entry=0x7fe93db8abd0, instance=instance@entry=0x5623c76ddd50, args=args@entry=0x7fe93db8acc8, n_params=2, param_types=0x5623c76ca940) at /home/smcv/src/glib/gobject/gclosure.c:867
#9  0x00007fe942638cc7 in g_signal_emit_valist (instance=0x5623c76ddd50, signal_id=<optimized out>, detail=0, var_args=var_args@entry=0x7fe93db8acc8) at /home/smcv/src/glib/gobject/gsignal.c:3300
#10 0x00007fe942639c24 in g_signal_emit (instance=instance@entry=0x5623c76ddd50, signal_id=<optimized out>, detail=detail@entry=0) at /home/smcv/src/glib/gobject/gsignal.c:3447
#11 0x00007fe9428ff2ed in g_threaded_socket_service_func (_data=0x5623c76c7f70, user_data=0x5623c76ddd50) at /home/smcv/src/glib/gio/gthreadedsocketservice.c:87
#12 0x00007fe941d56185 in g_thread_pool_thread_proxy (data=<optimized out>) at /home/smcv/src/glib/glib/gthreadpool.c:307
#13 0x00007fe941d55688 in g_thread_proxy (data=0x5623c76dcd40) at /home/smcv/src/glib/glib/gthread.c:784
#14 0x00007fe941851519 in start_thread (arg=0x7fe93db8b700) at pthread_create.c:456
#15 0x00007fe940ce6a4f in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97