elasticsearchwriter判断语句有误

在ESClient.java: 60行判断时是否有误
if (!("".equals(user) || "".equals(passwd))) {}
如果没有用户名或者密码，
会报
Preemptive authentication set without credentials provider 异常
判断逻辑应该是否应该修改一下

Start at ESClient.java line 60 and inspect the authentication condition used when the username or password is empty. Reproduce the Elasticsearch writer case without credentials and verify that it no longer raises “Preemptive authentication set without credentials provider” when the condition is corrected.

Written by the indexing model from the issue text.