Null pointer exception

[erfanegtfi]

I get Null pointer exception on Sheba.dart line 53, because bank.process is null

final data = bank.process!(shebaCode);

for a sheba number of City Bank

BankInformation? call() {
   final shebaCode = _shebaCode;
   if (!isValid) return null;
   final bankCode = patternCode.firstMatch(shebaCode)?[1] ?? '';
   var bank = banksInfo[bankCode];
   if (bank == null) return null;
   if (bank.isAccountNumberAvailable) {
     final data = bank.process!(shebaCode);
     bank.accountNumber = data.accountNumber;
     bank.formattedAccountNumber = data.formattedAccountNumber;
   }
   bank.process = null;
   return bank;
 }

persian_tools: ^1.0.3