qtractor hangs with QT6

It works with QT5 but hangs with QT6 like this: ``` $ qtractor (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.487: cannot register existing type 'GtkWidget' (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.488: cannot add class private field to invalid type '<invalid>' (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.488: cannot add private field to invalid (non-instantiatable) type '<invalid>' (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.488: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.488: cannot register existing type 'GtkBuildable' (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.488: g_type_interface_add_prerequisite: assertion 'G_TYPE_IS_INTERFACE (interface_type)' failed (<unknown>:12573): GLib-CRITICAL **: 11:04:04.488: g_once_init_leave: assertion 'result != 0' failed (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.488: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed (<unknown>:12573): Gtk-CRITICAL **: 11:04:04.488: gtk_widget_get_style_context: assertion 'GTK_IS_WIDGET (widget)' failed (<unknown>:12573): Gtk-CRITICAL **: 11:04:04.488: gtk_style_context_lookup_color: assertion 'GTK_IS_STYLE_CONTEXT (context)' failed (<unknown>:12573): Gtk-CRITICAL **: 11:04:04.488: gtk_style_context_get_background_color: assertion 'GTK_IS_STYLE_CONTEXT (context)' failed (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.488: cannot register existing type 'GtkWidget' (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.488: cannot add class private field to invalid type '<invalid>' (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.488: cannot add private field to invalid (non-instantiatable) type '<invalid>' (<unknown>:12573): GLib-GObject-CRITICAL **: 11:04:04.488: g_type_add_interface_static: assertion 'G_TYPE_IS_INSTANTIATABLE (instance_type)' failed ``` Window doesn't appear. Version: 1.5.8 FreeBSD 14.3