fix child_status assignment (#21784)

Author: evansmith

lib/pdf_fill/forms/va686c674v2.rb

@@ -1683,7 +1683,7 @@ def merge_child_helpers
       # rubocop:disable Metrics/MethodLength
       def expand_child_status(child)
         # expand child status
-        child_status = child['relationship_to_child']
+        child_status = child['relationship_to_child'] || {}
         date_entered_household = split_date(child['date_entered_household'])
 
         if child.key?('has_child_ever_been_married')