Following another user's Blog Dashboard link shows a list of that user's blogs. Clicking on one of the listed blogs produces unexpected results.

1. If USER1 is logged in and clicks on one of USER2's blogs from USER2's Blog Dashboard, USER1 sees a 404 page.
2. If a user who is not logged in clicks on one of any USER's blogs from USER's Blog Dashboard, the unauthenticated user sees SERVER ERROR.

This is caused by the below snippet of code.

mediagoblin/media_types/blog/views.py:

def blog_post_listing(request, page, url_user=None):
    """
    Page, listing all the blog posts of a particular blog.
    """
    blog_slug = request.matchdict.get('blog_slug', None)
    blog = get_blog_by_slug(request, blog_slug, author=request.user.id)
    if not blog:
        return render_404(request)

In case 1 above, request.user.id will become the id of USER1, so blog returns empty (unless, I assume, USER1 has an identical blog slug to USER2).

In case 2 above, request.user.id produces a server error with the following text:

Error - <type 'exceptions.AttributeError'>: 'NoneType' object has no attribute 'id'
URL: https://domain.tld/mediagoblin/u/USER/b/BLOG/
File '/path/to/mediagoblin/lib/python2.7/site-packages/Paste-1.7.5.1-py2.7.egg/paste/exceptions/errormiddleware.py', line 144 in __call__
  app_iter = self.application(environ, sr_checker)
File '/path/to/mediagoblin/lib/python2.7/site-packages/Paste-1.7.5.1-py2.7.egg/paste/urlmap.py', line 203 in __call__
  return app(environ, start_response)
File '/path/to/mediagoblin/mediagoblin/app.py', line 265 in __call__
  return self.call_backend(environ, start_response)
File '/path/to/mediagoblin/mediagoblin/app.py', line 242 in call_backend
  response = controller(request)
File '/path/to/mediagoblin/mediagoblin/decorators.py', line 114 in wrapper
  return controller(request, *args, url_user=user, **kwargs)
File '/path/to/mediagoblin/mediagoblin/decorators.py', line 165 in wrapper
  return controller(request, page=page, *args, **kwargs)
File '/path/to/mediagoblin/mediagoblin/media_types/blog/views.py', line 264 in blog_post_listing
  blog = get_blog_by_slug(request, blog_slug, author=request.user.id)
AttributeError: 'NoneType' object has no attribute 'id'

When deleting media that has comments and those comments have CommentNotification models, it seems to raise an error for those users. I can reproduce this by:

1. Create two users I'll call them "Chris" and "Tsyesika"
2. As Chris post an image
3. Login as Tsyesika and post a comment on said image
4. Make Tsyesika admin
5. Delete the image
6. Try to login as Chris

Those steps should trigger this exception:

Error - <class 'jinja2.exceptions.UndefinedError'>: 'mediagoblin.db.models.Graveyard object' has no attribute 'get_reply_to'
URL: https://dev.tsyesika.se/
File '/home/tsyesika/mediagoblin/lib/python2.7/site-packages/Paste-1.7.5.1-py2.7.egg/paste/exceptions/errormiddleware.py', line 144 in __call__
  app_iter = self.application(environ, sr_checker)
File '/home/tsyesika/mediagoblin/mediagoblin/app.py', line 342 in __call__
  return self.call_backend(environ, start_response)
File '/home/tsyesika/mediagoblin/lib/python2.7/site-packages/werkzeug/wsgi.py', line 591 in __call__
  return self.app(environ, start_response)
File '/home/tsyesika/mediagoblin/mediagoblin/app.py', line 276 in call_backend
  return self._finish_call_backend(request, environ, start_response)
File '/home/tsyesika/mediagoblin/mediagoblin/app.py', line 318 in _finish_call_backend
  response = controller(request)
File '/home/tsyesika/mediagoblin/mediagoblin/views.py', line 46 in root_view
  return view(request)
File '/home/tsyesika/mediagoblin/mediagoblin/decorators.py', line 47 in wrapper
  return controller(request, *args, **kwargs)
File '/home/tsyesika/mediagoblin/mediagoblin/decorators.py', line 170 in wrapper
  return controller(request, page=page, *args, **kwargs)
File '/home/tsyesika/mediagoblin/mediagoblin/views.py', line 37 in default_root_view
  'pagination': pagination})
File '/home/tsyesika/mediagoblin/mediagoblin/tools/response.py', line 36 in render_to_response
  render_template(request, template, context),
File '/home/tsyesika/mediagoblin/mediagoblin/tools/template.py', line 144 in render_template
  rendered = template.render(context)
File '/home/tsyesika/mediagoblin/lib/python2.7/site-packages/Jinja2-2.8-py2.7.egg/jinja2/environment.py', line 989 in render
  return self.environment.handle_exception(exc_info, True)
File '/home/tsyesika/mediagoblin/lib/python2.7/site-packages/Jinja2-2.8-py2.7.egg/jinja2/environment.py', line 754 in handle_exception
  reraise(exc_type, exc_value, tb)
File '/home/tsyesika/mediagoblin/mediagoblin/templates/mediagoblin/root.html', line 22 in top-level template code
  {% set feed_url = request.urlgen('mediagoblin.listings.atom_feed') %}
File '/home/tsyesika/mediagoblin/mediagoblin/templates/mediagoblin/base.html', line 67 in top-level template code
  {% block mediagoblin_body %}
File '/home/tsyesika/mediagoblin/mediagoblin/templates/mediagoblin/base.html', line 69 in block "mediagoblin_body"
  {% block mediagoblin_header %}
File '/home/tsyesika/mediagoblin/mediagoblin/templates/mediagoblin/base.html', line 183 in block "mediagoblin_header"
  {% include 'mediagoblin/fragments/header_notifications.html' %}
File '/home/tsyesika/mediagoblin/mediagoblin/templates/mediagoblin/fragments/header_notifications.html', line 9 in top-level template code
  {% set media = comment.get_reply_to() %}
UndefinedError: 'mediagoblin.db.models.Graveyard object' has no attribute 'get_reply_to'