backtrace of a strange weston_mode_switch()

gistfile1.txt

(gdb) bt
#0  weston_output_switch_mode (output=0x642590, mode=0x0, scale=1, op=WESTON_MODE_SWITCH_RESTORE_NATIVE)
    at ../../src/compositor.c:108
#1  0x00007ffff018af01 in restore_output_mode (output=0x642590) at ../../src/shell.c:1632
#2  0x00007ffff018af38 in restore_all_output_modes (compositor=0x6412d0) at ../../src/shell.c:1644
#3  0x00007ffff018e2b0 in activate (shell=0x643770, es=0x6c9f70, seat=0x694a08) at ../../src/shell.c:3097
#4  0x00007ffff018f300 in map (shell=0x643770, surface=0x6c9f70, width=806, height=491, sx=0, sy=0)
    at ../../src/shell.c:3573
#5  0x00007ffff018f5fe in shell_surface_configure (es=0x6c9f70, sx=0, sy=0, width=806, height=491)
    at ../../src/shell.c:3660
#6  0x000000000040c475 in weston_surface_commit (surface=0x6c9f70) at ../../src/compositor.c:1662
#7  0x000000000040c6e8 in surface_commit (client=0x6b38d0, resource=0x6ca2d0) at ../../src/compositor.c:1732
#8  0x00007ffff65b9c18 in ffi_call_unix64 () from /usr/lib/x86_64-linux-gnu/libffi.so.6
#9  0x00007ffff65b9580 in ffi_call () from /usr/lib/x86_64-linux-gnu/libffi.so.6
#10 0x00007ffff7bd3816 in wl_closure_invoke (closure=0x6c68c0, flags=2, target=0x6ca2d0, opcode=6, data=0x6b38d0)
    at ../../src/connection.c:918
#11 0x00007ffff7bce5ce in wl_client_connection_data (fd=18, mask=1, data=0x6b38d0) at ../../src/wayland-server.c:332
#12 0x00007ffff7bd0a80 in wl_event_source_fd_dispatch (source=0x6c7fb0, ep=0x7fffffffdb30)
    at ../../src/event-loop.c:86
#13 0x00007ffff7bd1496 in wl_event_loop_dispatch (loop=0x633a60, timeout=-1) at ../../src/event-loop.c:421
#14 0x00007ffff7bcf53e in wl_display_run (display=0x6339d0) at ../../src/wayland-server.c:869
#15 0x0000000000410455 in main (argc=1, argv=0x7fffffffdf78) at ../../src/compositor.c:3541


(gdb) bt full
#0  weston_output_switch_mode (output=0x642590, mode=0x0, scale=1, op=WESTON_MODE_SWITCH_RESTORE_NATIVE)
    at ../../src/compositor.c:108
        seat = 0x6a5e20
        resource = 0x7fffffffd570
        old_output_region = {extents = {x1 = 7014184, y1 = 0, x2 = 7014208, y2 = 0}, data = 0x7fffffffd5a0}
        ret = 32767
        notify_mode_changed = 88
        notify_scale_changed = 0
        temporary_mode = 7014184
        temporary_scale = 0
#1  0x00007ffff018af01 in restore_output_mode (output=0x642590) at ../../src/shell.c:1632
No locals.
#2  0x00007ffff018af38 in restore_all_output_modes (compositor=0x6412d0) at ../../src/shell.c:1644
        output = 0x642590
#3  0x00007ffff018e2b0 in activate (shell=0x643770, es=0x6c9f70, seat=0x694a08) at ../../src/shell.c:3097
        main_surface = 0x6c9f70
        state = 0x6b0700
        ws = 0x0
#4  0x00007ffff018f300 in map (shell=0x643770, surface=0x6c9f70, width=806, height=491, sx=0, sy=0)
    at ../../src/shell.c:3573
        compositor = 0x6412d0
        shsurf = 0x6cd170
        surface_type = SHELL_SURFACE_TOPLEVEL
        parent = 0x7fffffffd8e0
        seat = 0x694a08
        ws = 0x643a50
        panel_height = 0
        surf_x = 7131504
        surf_y = 0
#5  0x00007ffff018f5fe in shell_surface_configure (es=0x6c9f70, sx=0, sy=0, width=806, height=491)
    at ../../src/shell.c:3660
        shsurf = 0x6cd170
        shell = 0x643770
        type_changed = 1
#6  0x000000000040c475 in weston_surface_commit (surface=0x6c9f70) at ../../src/compositor.c:1662
        opaque = {extents = {x1 = 0, y1 = 0, x2 = 7119568, y2 = 0}, data = 0x7fffffffd780}
        surface_width = 806
        surface_height = 491
#7  0x000000000040c6e8 in surface_commit (client=0x6b38d0, resource=0x6ca2d0) at ../../src/compositor.c:1732
        surface = 0x6c9f70
        sub = 0x0
#8  0x00007ffff65b9c18 in ffi_call_unix64 () from /usr/lib/x86_64-linux-gnu/libffi.so.6