VariableDoesNotExist error

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When I attempt to upload a new logo in the Settings panel, I get the following in my logs:

[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139] mod_wsgi (pid=17280): Exception occurred processing WSGI script '/opt/cell-reference/django.wsgi'.
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139] Traceback (most recent call last):
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]   File "/usr/local/lib/python2.6/dist-packages/django/core/handlers/wsgi.py", line 272, in __call__
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]     response = self.get_response(request)
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]   File "/usr/local/lib/python2.6/dist-packages/django/core/handlers/base.py", line 169, in get_response
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]     response = self.handle_uncaught_exception(request, resolver, sys.exc_info())
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]   File "/usr/local/lib/python2.6/dist-packages/django/core/handlers/base.py", line 218, in handle_uncaught_exception
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]     return callback(request, **param_dict)
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]   File "/usr/local/lib/python2.6/dist-packages/django/utils/decorators.py", line 93, in _wrapped_view
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]     response = view_func(request, *args, **kwargs)
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]   File "/usr/local/lib/python2.6/dist-packages/django/views/defaults.py", line 31, in server_error
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]     return http.HttpResponseServerError(t.render(Context({})))
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]   File "/usr/local/lib/python2.6/dist-packages/django/template/base.py", line 123, in render
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]     return self._render(context)
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]   File "/usr/local/lib/python2.6/dist-packages/django/template/base.py", line 117, in _render
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]     return self.nodelist.render(context)
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]   File "/usr/local/lib/python2.6/dist-packages/django/template/base.py", line 744, in render
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]     bits.append(self.render_node(node, context))
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]   File "/usr/local/lib/python2.6/dist-packages/django/template/base.py", line 757, in render_node
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]     return node.render(context)
[Thu Apr 19 14:55:08 2012] [error] [client 109.145.40.139]   File "/usr/local/lib/python2.6/dist-packages/askbot ...