fix(openaccount): 开户时初始化 balance=0

openAccount 建账户时未传 balance，account.balance 落 NULL，记账 leg_accounting 里
account.balance + balance_amount 报 TypeError NoneType+float。开户即记 0 余额。

accounting/openaccount.py

@@ -19,7 +19,8 @@ async def openAccount(sor, accounting_orgid, orgid, account_config, org1id=None)
 		'orgid':orgid,
 		'subjectid':account_config['subjectid'],
 		'balance_at':account_config['balance_side'],
-		'max_detailno':0
+		'max_detailno':0,
+		'balance': 0.0
 	}
 	if org1id:
 		ns['org1id'] = org1id;