fix(markdown): skip empty bold headings

pageindex/page_index_md.py

@@ -62,7 +62,8 @@ def extract_nodes_from_markdown(markdown_content):
             bold_match = re.match(bold_heading_pattern, stripped_line)
             if bold_match:
                 title = bold_match.group(1).strip()
-                node_list.append({'node_title': title, 'line_num': line_num, 'level': 1})
+                if title:
+                    node_list.append({'node_title': title, 'line_num': line_num, 'level': 1})
 
     return node_list, lines
 
@@ -340,4 +341,4 @@ if __name__ == "__main__":
     with open(output_path, 'w', encoding='utf-8') as f:
         json.dump(tree_structure, f, indent=2, ensure_ascii=False)
     
-    print(f"\nTree structure saved to: {output_path}")
+    print(f"\nTree structure saved to: {output_path}")

tests/test_page_index_md.py

@@ -0,0 +1,23 @@
+import unittest
+
+from pageindex.page_index_md import extract_nodes_from_markdown
+
+
+class ExtractNodesFromMarkdownTest(unittest.TestCase):
+    def test_skips_bold_heading_with_only_whitespace(self):
+        nodes, _ = extract_nodes_from_markdown("**   **\n**Valid heading**")
+
+        self.assertEqual(
+            nodes,
+            [
+                {
+                    "node_title": "Valid heading",
+                    "line_num": 2,
+                    "level": 1,
+                }
+            ],
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()