David King authored Jul 16, 2015 and Paolo Bacchilega committed Dec 13, 2015

Found with Valgrind:

==9376== 56 (40 direct, 16 indirect) bytes in 1 blocks are definitely
lost in loss record 10,629 of 17,916
==9376==    at 0x721CA3A: g_type_create_instance (gtype.c:1849)
==9376==    by 0x71FF0AA: g_object_new_internal (gobject.c:1774)
==9376==    by 0x72008C0: g_object_newv (gobject.c:1921)
==9376==    by 0x72011AB: g_object_new (gobject.c:1614)
==9376==    by 0x5301393: gtk_size_group_new (gtksizegroup.c:425)
==9376==    by 0x441548: fr_window_construct (fr-window.c:5740)
==9376==    by 0x441548: fr_window_new (fr-window.c:5796)
==9376==    by 0x41C490: fr_application_command_line
(fr-application.c:588)
==9376==    by 0xC750D2F: ffi_call_unix64 (in
/usr/lib64/libffi.so.6.0.2)
==9376==    by 0xC75079A: ffi_call (in /usr/lib64/libffi.so.6.0.2)
==9376==    by 0x71FAB94: g_cclosure_marshal_generic_va
(gclosure.c:1594)
==9376==    by 0x71FA0C3: _g_closure_invoke_va (gclosure.c:864)
==9376==    by 0x7213DD8: g_signal_emit_valist (gsignal.c:3246)
==9376==    by 0x72148F1: g_signal_emit (gsignal.c:3393)
==9376==    by 0x6F0CF82: g_application_call_command_line
(gapplication.c:953)
==9376==    by 0x6F0F55F: g_application_run (gapplication.c:2292)
==9376==    by 0x414FE5: main (main.c:38)

https://bugzilla.gnome.org/show_bug.cgi?id=752476