Fix null exception if dataset does not have notes
Fix null exception if dataset does not have notes

opencolorado/.NET-Wrapper-for-CKAN-API,opencolorado/.NET-Wrapper-for-CKAN-API,DenverDev/.NET-Wrapper-for-CKAN-API,DenverDev/.NET-Wrapper-for-CKAN-API,opencolorado/.NET-Wrapper-for-CKAN-API