Fixed 2 issues on form N-400

First fix: Part 6 - Children's info: allow zero children

Users with no children under 18 can now enter 0 and submit the form without filling in any child fields. Previously, all child row 1 fields were unconditionally required, blocking valid submissions.

File: children-info-map.js — added hasChildren() guard on all child row fields.

Second fix: Part 8 - Time outside the U.S.: allow no travel history

Users who have never traveled outside the United States can now leave all trip fields empty and submit the form. Previously, row 1 travel fields were unconditionally required, blocking valid submissions from applicants with no trips to report.

File: outside-usa-map.js — added hasTraveled() guard on all travel row fields.