Script help: Holiday edge case lead to empty datasets

[lrose]

@zacharyw.larson

I think "an error of calling a variable before it is defined" might be so common that there is a common solution.

There is, don't do it.

The problem here is that you are trying to index an empty list. You should make sure that there is data in the list prior to trying to access it if there is a chance that the list is empty.

#assuming that datasetIn is a pyDataSet
if datasetIn.rowCount:
    for row, nextRow in zip(datasetIn, datasetIn[1:]):