Comment 2 for bug 870792

StacktraceTop:
 g_type_check_instance_is_a (type_instance=<optimized out>, iface_type=<optimized out>) at /build/buildd/glib2.0-2.30.0/./gobject/gtype.c:3952
 nautilus_file_info_invalidate_extension_info (file=0x1bd5610) at nautilus-file-info.c:262
 file_watcher_update_path (watcher=0x1168870, path=0x2023180 "/home/christophe/Musique") at file-watcher.c:373
 g_closure_invoke (closure=0x124f370, return_value=0x0, n_param_values=3, param_values=0x7f3a50053cf0, invocation_hint=<optimized out>) at /build/buildd/glib2.0-2.30.0/./gobject/gclosure.c:774
 signal_emit_unlocked_R (node=<optimized out>, detail=0, instance=0x7f3a60002d00, emission_return=0x0, instance_and_params=0x7f3a50053cf0) at /build/buildd/glib2.0-2.30.0/./gobject/gsignal.c:3272