bugfix: crontab script fails when field 'covered_areas' is empty in isp.json.

Thx mycélium :)

ffdnispdb/models.py

@@ -265,7 +265,7 @@ class ISPWhoosh(object):
             'name': model.name,
             'shortname': model.shortname,
             'description': model.json.get('description'),
-            'covered_areas': ','.join(model.covered_areas_names()),
+            'covered_areas': unicode(','.join(model.covered_areas_names())),
             'step': model.json.get('progressStatus')
         }
         writer.update_document(**kw)