Error from summary endpoints aggregating by just year

[erika-tyagi]

Package throws an error if you try to aggregate summary endpoints by just year (i.e. without another grouping variable).

For example:

educationdata using "school ccd enrollment", summaries(sum enrollment by year) clear

or

educationdata using "college ipeds enrollment-full-time-equivalent", summaries(sum credit_hours by year)

throw an error saying variable year already defined because the year variable is already included in summary endpoint aggregations by default.