[BUG] ` gtk4::Paned.emit_cycle_handle_focus` cause crash

[qarmin]

System:    Host: rafalkom Kernel: 5.13.0-28-generic x86_64 bits: 64 compiler: gcc v: 11.2.0 Desktop: GNOME 40.5 
           tk: GTK 3.24.30 wm: gnome-shell dm: GDM3 Distro: Ubuntu 21.10 (Impish Indri) 

RUST_BACKTRACE=full RUSTFLAGS=-Zsanitizer=address RUSTDOCFLAGS=-Zsanitizer=address cargo run  -Zbuild-std --target x86_64-unknown-linux-gnu

Bug description

    let object_597 = Paned::default(); // Paned
    object_597.emit_cycle_handle_focus(true);

cause crash:

**
Gtk:ERROR:../../../gtk/gtkpaned.c:2187:gtk_paned_find_neighbours: assertion failed: (all_panes)
Bail out! Gtk:ERROR:../../../gtk/gtkpaned.c:2187:gtk_paned_find_neighbours: assertion failed: (all_panes)
Aborted (core dumped)

Issue found by fuzzer - https://github.com/qarmin/gtk-rs-fuzzer