Internal Server Error when saving a plot

[alexgleason]

Logs from the staging server:

2018-01-12T02:08:52.180864172Z app[web.1]: Internal Server Error: /plot/9/edit/
2018-01-12T02:08:52.180872030Z app[web.1]: Traceback (most recent call last):
2018-01-12T02:08:52.180879941Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/core/handlers/exception.py", line 35, in inner
2018-01-12T02:08:52.180889350Z app[web.1]:     response = get_response(request)
2018-01-12T02:08:52.180938572Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/core/handlers/base.py", line 128, in _get_response
2018-01-12T02:08:52.180963607Z app[web.1]:     response = self.process_exception_by_middleware(e, request)
2018-01-12T02:08:52.180972878Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/core/handlers/base.py", line 126, in _get_response
2018-01-12T02:08:52.181018582Z app[web.1]:     response = wrapped_callback(request, *callback_args, **callback_kwargs)
2018-01-12T02:08:52.181033139Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/views/generic/base.py", line 69, in view
2018-01-12T02:08:52.181041968Z app[web.1]:     return self.dispatch(request, *args, **kwargs)
2018-01-12T02:08:52.181050262Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/contrib/auth/mixins.py", line 52, in dispatch
2018-01-12T02:08:52.181060168Z app[web.1]:     return super().dispatch(request, *args, **kwargs)
2018-01-12T02:08:52.181107259Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/contrib/auth/mixins.py", line 109, in dispatch
2018-01-12T02:08:52.181144074Z app[web.1]:     return super().dispatch(request, *args, **kwargs)
2018-01-12T02:08:52.181152882Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/views/generic/base.py", line 89, in dispatch
2018-01-12T02:08:52.181161028Z app[web.1]:     return handler(request, *args, **kwargs)
2018-01-12T02:08:52.181213635Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/views/generic/edit.py", line 194, in post
2018-01-12T02:08:52.181223392Z app[web.1]:     return super().post(request, *args, **kwargs)
2018-01-12T02:08:52.181231758Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/views/generic/edit.py", line 141, in post
2018-01-12T02:08:52.181240483Z app[web.1]:     if form.is_valid():
2018-01-12T02:08:52.181248100Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/forms/forms.py", line 179, in is_valid
2018-01-12T02:08:52.181287092Z app[web.1]:     return self.is_bound and not self.errors
2018-01-12T02:08:52.181297112Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/forms/forms.py", line 174, in errors
2018-01-12T02:08:52.181302818Z app[web.1]:     self.full_clean()
2018-01-12T02:08:52.181307806Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/forms/forms.py", line 376, in full_clean
2018-01-12T02:08:52.181313323Z app[web.1]:     self._clean_fields()
2018-01-12T02:08:52.181318289Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/forms/forms.py", line 394, in _clean_fields
2018-01-12T02:08:52.181323780Z app[web.1]:     value = field.clean(value)
2018-01-12T02:08:52.181328803Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/forms/fields.py", line 148, in clean
2018-01-12T02:08:52.181334195Z app[web.1]:     value = self.to_python(value)
2018-01-12T02:08:52.181339123Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/forms/models.py", line 1245, in to_python
2018-01-12T02:08:52.181375275Z app[web.1]:     value = self.queryset.get(**{key: value})
2018-01-12T02:08:52.181382069Z app[web.1]:   File "/usr/local/lib/python3.5/site-packages/django/db/models/query.py", line 407, in get
2018-01-12T02:08:52.181387709Z app[web.1]:     (self.model._meta.object_name, num)
2018-01-12T02:08:52.181392821Z app[web.1]: gardenhub.models.MultipleObjectsReturned: get() returned more than one Garden -- it returned 2!