[Bugfix] 修复配置ldap登录，并设置auth-user-registration: false的空指针异常

configure LDAP authentication and set auth-user-registration: false, result in NPE(Null Pointer Exception) didi#1116

Author: weidong_chang

km-extends/km-account/src/main/java/com/xiaojukeji/know/streaming/km/account/login/ldap/LdapLoginServiceImpl.java

@@ -18,7 +18,6 @@
 import com.xiaojukeji.know.streaming.km.account.login.ldap.remote.LdapAuthentication;
 import com.xiaojukeji.know.streaming.km.common.constant.Constant;
 import com.xiaojukeji.know.streaming.km.common.utils.CommonUtils;
-import com.xiaojukeji.know.streaming.km.common.utils.ConvertUtil;
 import com.xiaojukeji.know.streaming.km.common.utils.ValidateUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;