Fix GTK build

* src/xterm.c (x_dnd_begin_drag_and_drop) [USE_GTK]: Adjust call
to x_dnd_free_toplevels as well.
2 jobs for master in 81 minutes (queued for 7 seconds)
Status Job ID Name Coverage
  Build Images
failed #46707
build-image-inotify

01:21:00

 
  Normal
skipped #46708
test-src-inotify
 
Name Stage Failure
failed
build-image-inotify Build Images
 > [emacs-inotify 5/5] RUN make bootstrap:
------
executor failed running [/bin/sh -c make bootstrap]: exit code: 2
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
$ find ${test_name} ! \( -name "*.log" -o -name ${EMACS_TEST_JUNIT_REPORT} \) -type f -delete
find: build-image-inotify-2340243a: No such file or directory
ERROR: Job failed: exit code 1