gnucash2ledger: -s option triggers AttributeError: 'NoneType' object has no attribute 'upper'

[jmarshallidau]

If invoked with -s gnucash2ledger emits the following error. The attached patch "fixes" the problem in that the -s functionality now works, but I'm sure it's not the proper soution. I'm not a python programmer but I'm guessing it's some kind of type mismatch with "None".

Error

Traceback (most recent call last):
  File "/Users/john/rwfin/2022/gnucash2ledger.py", line 791, in <module>
    main()
  File "/Users/john/rwfin/2022/gnucash2ledger.py", line 778, in main
    convertor = LedgerConvertor(args)
  File "/Users/john/rwfin/2022/gnucash2ledger.py", line 482, in __init__
    self.gcashData = GnucashData(
  File "/Users/john/rwfin/2022/gnucash2ledger.py", line 453, in __init__
    Account(self.accountDb, acc, useSymbols=useSymbols)
  File "/Users/john/rwfin/2022/gnucash2ledger.py", line 120, in __init__
    self.commodity = get_currency_symbol(
  File "/Users/john/rwfin/2022/gnucash2ledger.py", line 594, in get_currency_symbol
    return CurrencySymbols.get_symbol(currency_code) or currency_code
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/currency_symbols/currency_symbols.py", line 23, in get_symbol
    return CURRENCY_SYMBOLS_MAP.get(currency.upper(), None)
AttributeError: 'NoneType' object has no attribute 'upper'

Patch

currency_code.diff.txt