[Bug: 21.4.22] Assertion failed in window_loop

================================================================ Dear Bug Team! Xemacs aborted after running C-x C-b (list-buffers). The buffer list was previously shown and somehow hidden (by C-x1 or by other means.) This behaviour has been seen when invoking other commands which tries to show other buffers (for example vc-diff.) I had currently two frames open on two different screens (different $DISPLAY values.) C stack backtrace: (gdb) where #0 0xfe7a9bf7 in kill () from /lib/libc.so.1 #1 0x080b288a in fatal_error_signal (sig=6) at emacs.c:642 #2 0xfe7a73df in __sighndlr () from /lib/libc.so.1 #3 0xfe79d0f1 in call_user_handler () from /lib/libc.so.1 #4 <signal handler called> #5 0xfe7aa067 in _lwp_kill () from /lib/libc.so.1 #6 0xfe7a57c4 in thr_kill () from /lib/libc.so.1 #7 0xfe751da3 in raise () from /lib/libc.so.1 #8 0xfe731b84 in abort () from /lib/libc.so.1 #9 0x080b2d8b in assert_failed (file=0xfe81d000 "8Ø\021", line=-25517977, expr=0x0) at emacs.c:3426 #10 0x081a7dd8 in window_loop (type=GET_BUFFER_WINDOW, obj=154225152, mini=1, which_frames=154225152, dedicated_too=1, which_devices=136554500) at window.c:2649