When no plots are selected, export throws an error
If no plots are selected, exporting EEP simple reports throws an error, because there is no data to transfer to Excel. Could be checked in a couple of ways:
1) if there are no plots, don't even try to write anything to Excel
2) if .EOF on a query, don't transfer info to spreadsheet.
The actual error occurs just after "Vigor by spp." worksheet is written.