Get content from index 0 if Index section does not exist

scripts/validate/links.py

@@ -29,6 +29,8 @@ def find_links_in_file(filename: str) -> List[str]:
     with open(filename, mode='r', encoding='utf-8') as file:
         readme = file.read()
         index_section = readme.find('## Index')
+        if index_section == -1:
+            index_section = 0
         content = readme[index_section:]
 
     links = find_links_in_text(content)