Update main_statements.md

Author: flexferrum

docs/usage/main_statements.md

@@ -70,6 +70,7 @@ I.e. left part of this expression (before 'if') is a true-branch of the statemen
 {% for child in children_list %}
   {% if child = page.parent %}
   {% assign parent_page_info = child %}
+  {% endif %}
   {% if child.parent == page.parent and  child.title == page.title %}
     child.nav_order = {{ child.nav_order }}</br>
     child.url = {{ child.url }}</br>