Sphinx crashed when enabling sphinxcontrib-trimblank

[tk0miya]

Describe the bug
Sphinx crashed when enabling sphinxcontrib-trimblank

To Reproduce

Traceback (most recent call last):
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/cmd/build.py", line 276, in build_main
    app.build(args.force_all, filenames)
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/application.py", line 349, in build
    self.builder.build_update()
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/builders/__init__.py", line 299, in build_update
    len(to_build))
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/builders/__init__.py", line 361, in build
    self.write(docnames, list(updated_docnames), method)
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/builders/__init__.py", line 535, in write
    self._write_serial(sorted(docnames))
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/builders/__init__.py", line 542, in _write_serial
    doctree = self.env.get_and_resolve_doctree(docname, self)
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/environment/__init__.py", line 537, in get_and_resolve_doctree
    self.apply_post_transforms(doctree, docname)
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/environment/__init__.py", line 588, in apply_post_transforms
    self.events.emit('doctree-resolved', doctree, docname)
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/events.py", line 99, in emit
    results.append(callback(self.app, *args))
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/ext/todo.py", line 158, in __init__
    self.process(doctree, docname)
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/ext/todo.py", line 178, in process
    self.env.resolve_references(new_todo, todo['docname'], self.builder)  # type: ignore  # NOQA
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/environment/__init__.py", line 571, in resolve_references
    self.apply_post_transforms(doctree, fromdocname)
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/environment/__init__.py", line 588, in apply_post_transforms
    self.events.emit('doctree-resolved', doctree, docname)
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinx/events.py", line 99, in emit
    results.append(callback(self.app, *args))
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/sphinxcontrib/trimblank.py", line 122, in trimblank
    doctree.walk(visitor)
  File "/home/gohki/.venv/sphinx/lib/python3.7/site-packages/docutils/nodes.py", line 129, in walk
    visitor.document.reporter.debug(
AttributeError: 'todo_node' object has no attribute 'reporter'

Expected behavior
Build successfully.

Your project
https://github.com/sphinxjp/sphinx-users.jp

Screenshots
N/A

Environment info

• OS: Mac
• Python version: 3.8.1
• Sphinx version: 2.4.2
• Sphinx extensions: sphinxcontrib.trimblank
• Extra tools: Nothing

reported by @usaturn (thanks!)