sequencer.c: plug leaks in do_pick_commit

Going to leave, we additionally free the author and commit message
and make sure to call update_abort_safety_file().

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: stefanbeller

sequencer.c

@@ -1772,7 +1772,8 @@ static int do_pick_commit(enum todo_command command, struct commit *commit,
 		res = do_recursive_merge(base, next, base_label, next_label,
 					 &head, &msgbuf, opts);
 		if (res < 0)
-			return res;
+			goto leave;
+
 		res |= write_message(msgbuf.buf, msgbuf.len,
 				     git_path_merge_msg(), 0);
 	} else {