Fix bug in structure(), which reports list index out of bounds when a 'nan' is in a column
Fix bug in structure(), which reports list index out of bounds when a 'nan' is in a column

mathemage/h2o-3,h2oai/h2o-3,h2oai/h2o-3,spennihana/h2o-3,mathemage/h2o-3,h2oai/h2o-dev,h2oai/h2o-3,jangorecki/h2o-3,h2oai/h2o-dev,mathemage/h2o-3,jangorecki/h2o-3,michalkurka/h2o-3,spennihana/h2o-3,jangorecki/h2o-3,jangorecki/h2o-3,h2oai/h2o-3,spennihana/h2o-3,jangorecki/h2o-3,michalkurka/h2o-3,spennihana/h2o-3,mathemage/h2o-3,h2oai/h2o-3,spennihana/h2o-3,michalkurka/h2o-3,h2oai/h2o-dev,michalkurka/h2o-3,michalkurka/h2o-3,michalkurka/h2o-3,h2oai/h2o-3,spennihana/h2o-3,jangorecki/h2o-3,h2oai/h2o-dev,michalkurka/h2o-3,h2oai/h2o-dev,h2oai/h2o-dev,mathemage/h2o-3,jangorecki/h2o-3,mathemage/h2o-3,spennihana/h2o-3,mathemage/h2o-3,h2oai/h2o-dev,h2oai/h2o-3,h2oai/h2o-3