(gdb) bt
#0  0x00007f1814ed922a in XQueryTree (dpy=0x55cf9bc2e270, w=w@entry=0, root=root@entry=0x7ffcf50904b0, parent=parent@entry=0x7ffcf50904c0, children=children@entry=0x7ffcf50904d0, nchildren=nchildren@entry=0x7ffcf50904a0) at /usr/src/debug/libX11-1.8.7/src/QuTree.c:45
#1  0x000055cf99fa31b5 in find_wm_window (window=0x55cf9be22800) at ../src/screenshot-backend-x11.c:91
#2  screenshot_backend_x11_get_pixbuf (backend=<optimized out>, rectangle=0x0) at ../src/screenshot-backend-x11.c:363
#3  0x000055cf99fa4e9d in screenshot_get_pixbuf (rectangle=0x0) at ../src/screenshot-utils.c:66
#4  finish_take_screenshot (self=0x55cf9bc0ac50, self@entry=0x55cf9be69870) at ../src/screenshot-application.c:486
#5  take_screenshot_timeout (user_data=user_data@entry=0x55cf9bc0ac50) at ../src/screenshot-application.c:539
#6  0x00007f1814d99124 in g_timeout_dispatch (source=0x55cf9bd2e340, callback=0x55cf99fa4e30 <take_screenshot_timeout>, user_data=0x55cf9bc0ac50) at ../glib/gmain.c:4989
#7  0x00007f1814d96710 in g_main_dispatch (context=0x55cf9bc0d950) at ../glib/gmain.c:3344
#8  g_main_context_dispatch_unlocked (context=context@entry=0x55cf9bc0d950) at ../glib/gmain.c:4152
#9  0x00007f1814d98358 in g_main_context_iterate_unlocked (context=context@entry=0x55cf9bc0d950, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../glib/gmain.c:4217
#10 0x00007f1814d98a0c in g_main_context_iteration (context=context@entry=0x55cf9bc0d950, may_block=may_block@entry=1) at ../glib/gmain.c:4282
#11 0x00007f18141c494d in g_application_run (application=application@entry=0x55cf9bc0ac50, argc=argc@entry=2, argv=argv@entry=0x7ffcf5090828) at ../gio/gapplication.c:2712
#12 0x000055cf99fa115f in main (argc=2, argv=0x7ffcf5090828) at ../src/gnome-screenshot.c:47