Viewing data in dashboard complains when expocode is missing

[karlmsmith]

A check of the expocode given as a data column is made against only the first line of a dataset; the remaining lines can be blank. But when examining the data in the dashboard GUI, it gives an error dialog when displaying anything except the first piece of the dataset (with the first line with the expocode). This check of the expocode should only be done on upload, not when examining the data in the dashboard.