读取节点信息提示缺少对象

VB code

REST_RESPONSE = PostHttpPage(topurl, postdatastr)

Set xml=Server.CreateObject("Microsoft.XMLDOM")
    xml.Async=False
    xml.ValidateOnParse=False
    xml.LoadXml(REST_RESPONSE)
    If xml.ReadyState>2 Then
        Set item=xml.getElementsByTagName("trade")
        'response.Write(item.Length)
        If item.Length > 0 Then 
            For i=0 To (item.Length-1)
                    Set seller_memo=item.Item(i).getElementsByTagName("seller_memo")
                    Set receiver_address=item.Item(i).getElementsByTagName("receiver_address")
                    set receiver_name=item.Item(i).getElementsByTagName("receiver_name")
                    set receiver_state=item.Item(i).getElementsByTagName("receiver_state")
                    set receiver_city=item.Item(i).getElementsByTagName("receiver_city")
                    set receiver_district=item.Item(i).getElementsByTagName("receiver_district")
                    set receiver_mobile=item.Item(i).getElementsByTagName("receiver_mobile")
                    set receiver_phone=item.Item(i).getElementsByTagName("receiver_phone")
                    set receiver_zip=item.Item(i).getElementsByTagName("receiver_zip")
                
                    seller_memo_str=seller_memo.Item(0).Text   '这里提示缺少对象，因为这个字段为空，我要如何来判断这个对象是否存在
                    receiver_name_str=receiver_name.Item(0).Text
                    receiver_state_str=receiver_state.Item(0).Text
                    receiver_address_str=receiver_address.Item(0).Text
                    receiver_city_str=receiver_city.Item(0).Text
                    receiver_district_str=receiver_district.Item(0).Text
                    receiver_mobile_str=receiver_mobile.Item(0).Text
                    If receiver_phone is not nothing Then   
                    receiver_phone_str=receiver_phone.Item(0).Text
                    end if
                    receiver_zip_str=receiver_zip.Item(0).Text
            next
        end if
    end if
    set xml=nothing

代码如上，但是seller_memo_str=seller_memo.Item(0).Text '这里提示缺少对象，因为这个节点可能为空，我要如何来判断这个对象是否存在

谁给我解答一下啊，谢谢了

If seller_memo Is Nothing And seller_memo.Item(0) is Nothing Then
Else
End If