bw: fetchBalance: python needs currencyId to be a string

js/bw.js

@@ -607,7 +607,7 @@ module.exports = class bw extends Exchange {
         const result = { 'info': response };
         for (let i = 0; i < balances.length; i++) {
             const balance = balances[i];
-            const currencyId = this.safeInteger (balance, 'currencyTypeId');
+            const currencyId = this.safeString (balance, 'currencyTypeId');
             const code = this.safeCurrencyCode (currencyId);
             const account = this.account ();
             account['free'] = this.safeFloat (balance, 'amount');