in parser(), taking a subscript of the filter output would fail with an
IndexError exception.  Moving the check (in the form of a length check on
the filename variable) alleviates the potential for this exception.

This was noticed when running xlsx2csv against test/datetime.xlsx
in parser(), taking a subscript of the filter output would fail with an
IndexError exception.  Moving the check (in the form of a length check on
the filename variable) alleviates the potential for this exception.

This was noticed when running xlsx2csv against test/datetime.xlsx
Merge pull request #40 from gladiatr72/parse_function_fix

Parse function fix