Filter out blank config items in to_list().
Filter out blank config items in to_list().

ehealthafrica-ci/rapidsms,dimagi/rapidsms,rapidsms/rapidsms-core-dev,peterayeni/rapidsms,lsgunth/rapidsms,lsgunth/rapidsms,catalpainternational/rapidsms,caktus/rapidsms,unicefuganda/edtrac,eHealthAfrica/rapidsms,ken-muturi/rapidsms,caktus/rapidsms,dimagi/rapidsms-core-dev,peterayeni/rapidsms,ken-muturi/rapidsms,eHealthAfrica/rapidsms,caktus/rapidsms,unicefuganda/edtrac,lsgunth/rapidsms,eHealthAfrica/rapidsms,catalpainternational/rapidsms,peterayeni/rapidsms,ehealthafrica-ci/rapidsms,lsgunth/rapidsms,dimagi/rapidsms,ehealthafrica-ci/rapidsms,catalpainternational/rapidsms,unicefuganda/edtrac,dimagi/rapidsms-core-dev,peterayeni/rapidsms,ken-muturi/rapidsms,rapidsms/rapidsms-core-dev,catalpainternational/rapidsms