Segfault when using -w / --window to screenshot current window.

The gnome-screenshot program segfaults every time, when I try to capture the current window with `gnome-screenshot -w`. Taking an area screenshot with `gnome-screenshot -a`, and taking a full desktop screenshot with `gnome-screenshot` works, but taking a current window screenshot with `gnome-screenshot -w` segfaults every time. Adding delay with `-d <delay>` and capturing pointer or not with `-p` has no effect.

This may be the same bug as

https://bugs.launchpad.net/ubuntu/+source/gnome-screenshot/+bug/81817

although that one is closed long ago. The relationship is that I'm using gnome-screenshot inside the XMonad window manager, a non-standard window manager.

Stack trace:

$ gdb gnome-screenshot
GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1
[...]
Reading symbols from gnome-screenshot...(no debugging symbols found)...done.
(gdb) core-file core
warning: core file may not match specified executable file.
[New LWP 25469]
[New LWP 25472]
[New LWP 25470]
[New LWP 25471]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `gnome-screenshot -d 3 -w -p'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x000000000040dbb5 in ?? ()
[Current thread is 1 (Thread 0x7f3b4c841a40 (LWP 25469))]
(gdb) where
#0 0x000000000040dbb5 in ?? ()
#1 0x000000000040e1ea in ?? ()
#2 0x0000000000408bc1 in ?? ()
#3 0x0000000000408df9 in ?? ()
#4 0x00007f3b4a5afac3 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#5 0x00007f3b4a5af05a in g_main_context_dispatch ()
   from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#6 0x00007f3b4a5af400 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#7 0x00007f3b4a5af4ac in g_main_context_iteration ()
   from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#8 0x00007f3b4ab76cdd in g_application_run ()
   from /usr/lib/x86_64-linux-gnu/libgio-2.0.so.0
#9 0x0000000000408385 in ?? ()
#10 0x00007f3b49a84830 in __libc_start_main (main=0x408320, argc=5,
    argv=0x7fff78989e68, init=<optimized out>, fini=<optimized out>,
    rtld_fini=<optimized out>, stack_end=0x7fff78989e58)
    at ../csu/libc-start.c:291
#11 0x00000000004083c9 in ?? ()

System information:

$ lsb_release -rd
Description: Ubuntu 16.04.1 LTS
Release: 16.04

$ apt-cache policy gnome-screenshot
gnome-screenshot:
  Installed: 3.18.0-1ubuntu2
  Candidate: 3.18.0-1ubuntu2
  Version table:
 *** 3.18.0-1ubuntu2 500
        500 http://vault.galois.com/ubuntu xenial/main amd64 Packages
        100 /var/lib/dpkg/status