Internal Server Error if 'Sync URL' Setting has a preceding whitespace (or is not a URL)

2015-09-23 16:06:35 [HTTPChannel,439,127.0.0.1] 500 Error - /MAAS/settings/
        Traceback (most recent call last):
          File "/usr/lib/django16/django/core/handlers/wsgi.py", line 206, in __call__
            response = self.get_response(request)
          File "/usr/lib/python2.7/dist-packages/maasserver/utils/views.py", line 236, in get_response
            response = get_response(request)
          File "/usr/lib/python2.7/dist-packages/maasserver/utils/views.py", line 210, in get_response
            return django_get_response(request)
          File "/usr/lib/django16/django/core/handlers/base.py", line 194, in get_response
            response = self.handle_uncaught_exception(request, resolver, sys.exc_info())
        --- <exception caught here> ---
          File "/usr/lib/django16/django/core/handlers/base.py", line 112, in get_response
            response = wrapped_callback(request, *callback_args, **callback_kwargs)
          File "/usr/lib/python2.7/dist-packages/maasserver/utils/views.py", line 189, in view_atomic_with_post_commit_savepoint
            return view_atomic(*args, **kwargs)
          File "/usr/lib/django16/django/db/transaction.py", line 371, in inner
            return func(*args, **kwargs)
          File "/usr/lib/django16/django/contrib/auth/decorators.py", line 22, in _wrapped_view
            return view_func(request, *args, **kwargs)
          File "/usr/lib/python2.7/dist-packages/maasserver/views/settings.py", line 205, in settings
            'boot_source', "Configuration updated.")
          File "/usr/lib/python2.7/dist-packages/maasserver/views/__init__.py", line 219, in process_form
            form.save()
          File "/usr/lib/python2.7/dist-packages/maasserver/forms.py", line 1435, in save
            boot_source.save()
          File "/usr/lib/python2.7/dist-packages/maasserver/models/cleansave.py", line 37, in save
            self.full_clean()
          File "/usr/lib/django16/django/db/models/base.py", line 950, in full_clean
            raise ValidationError(errors)
        django.core.exceptions.ValidationError: {'url': [u'Enter a valid URL.']}