模拟单，平仓操作提示错误

测试过程：1、首先把快期模拟账户手动平仓，使仓位归0. 2、运行代码：发出金叉买入信号，要求平掉账号所有空单，然后下1手多单。

3、运行结果，因为账号本来就空仓，所以下一手多单正常完成。  4、信号死叉做空，要求先平掉账户多单，再下一首空单。运行结果，提示：平仓单错误，又下的一张空单正确。请老师指导。

if D.iloc[-2] < B.iloc[-2] and D.iloc[-1] > B.iloc[-1]:
            print("死叉")
            #获取持仓量，大于零就先平仓，再开空单1手，持仓量等于零，直接开空单1手
            position = api.get_position(SYMBOL)
            if position.pos_long > 0:
                order1 = api.insert_order(symbol=SYMBOL, direction="SELL", offset="CLOSE", volume=position.pos_long,limit_price=klines.iloc[-1].close-1)
                order2 = api.insert_order(symbol=SYMBOL, direction="SELL", offset="OPEN", volume=1,limit_price=klines.iloc[-1].close - 1)
             else:
                order2 = api.insert_order(symbol=SYMBOL, direction="SELL", offset="OPEN", volume=1,limit_price = klines.iloc[-1].close-1)
         if D.iloc[-2] > B.iloc[-2] and D.iloc[-1] < B.iloc[-1]:
            print("金叉")
            #获取持仓量，大于零就先平仓，再开多单，等于零就直接开1手多单。
            position = api.get_position(SYMBOL)
            if position.pos_short > 0:
                order1 = api.insert_order(symbol=SYMBOL, direction="BUY", offset="CLOSE",volume=position.pos_short,limit_price=klines.iloc[-1].close+1)
                order2 = api.insert_order(symbol=SYMBOL, direction="BUY", offset="OPEN", volume=1,limit_price=klines.iloc[-1].close + 1)
             else:
                order2 = api.insert_order(symbol=SYMBOL, direction="BUY", offset="OPEN", volume=1,limit_price = klines.iloc[-1].close+1)