„Add Media“ Button is hidden First you need to click small arrow icon in the upper right to open a hidden area where you can find this button

The Add to Collection page provides a pre-populated dropdown list of collections to which media can be added. By default, the dropdown box says "-- Select --." If you click Add without selecting a collection, a server error is generated with the following traceback.

2017-06-28 21:30:46,445 ERROR   [waitress] Exception when serving /u/andrew/m/1/collect/
Traceback (most recent call last):
  File "/path/to/mediagoblin/lib/python2.7/site-packages/waitress-1.0a1-py2.7.egg/waitress/channel.py", line 338, in service
    task.service()
  File "/path/to/mediagoblin/lib/python2.7/site-packages/waitress-1.0a1-py2.7.egg/waitress/task.py", line 169, in service
    self.execute()
  File "/path/to/mediagoblin/lib/python2.7/site-packages/waitress-1.0a1-py2.7.egg/waitress/task.py", line 399, in execute
    app_iter = self.channel.server.application(env, start_response)
  File "/path/to/mediagoblin/mediagoblin/app.py", line 342, in __call__
    return self.call_backend(environ, start_response)
  File "/path/to/mediagoblin/lib/python2.7/site-packages/Werkzeug-0.11.10-py2.7.egg/werkzeug/wsgi.py", line 599, in __call__
    return self.app(environ, start_response)
  File "/path/to/mediagoblin/mediagoblin/app.py", line 276, in call_backend
    return self._finish_call_backend(request, environ, start_response)
  File "/path/to/mediagoblin/mediagoblin/app.py", line 318, in _finish_call_backend
    response = controller(request)
  File "/path/to/mediagoblin/mediagoblin/decorators.py", line 47, in wrapper
    return controller(request, *args, **kwargs)
  File "/path/to/mediagoblin/mediagoblin/decorators.py", line 280, in wrapper
    return controller(request, media=media, *args, **kwargs)
  File "/path/to/mediagoblin/mediagoblin/decorators.py", line 47, in wrapper
    return controller(request, *args, **kwargs)
  File "/path/to/mediagoblin/mediagoblin/decorators.py", line 74, in new_controller_func
    return controller(request, *args, **kwargs)
  File "/path/to/mediagoblin/mediagoblin/user_pages/views.py", line 300, in media_collect
    item = CollectionItem.query.filter_by(collection=collection.id)
AttributeError: 'NoneType' object has no attribute 'id'