Merge pull request #8937 from jantonguirao/fix_explicit_title_subpages

Use explicit title instead of <no title> in the title bar of subpages

sphinx/environment/collectors/title.py

@@ -50,7 +50,7 @@ def process_doc(self, app: Sphinx, doctree: nodes.document) -> None:
             break
         else:
             # document has no title
-            titlenode += nodes.Text('<no title>')
+            titlenode += nodes.Text(doctree.get('title', '<no title>'))
         app.env.titles[app.env.docname] = titlenode
         app.env.longtitles[app.env.docname] = longtitlenode