Creates empty .csv file for sheet not found

[billsker]

It seems, unless I'm interpreting this incorrectly, that

Xlsx2csv('file.xlsx',sheetid=4).convert(sheet4.csv,sheetid=4)

creates an empty csv file called "sheet4.csv" even if there is no sheet in the xlsx file with sheetid=4. It seems to create the file, THEN raise the exception.

The command-line version works as expected, and returns the "Sheet with index 4 not found or can't be handled" message without actually creating the sheet4.csv file.