用户不存在时，登录报错不正确

doc-framework/src/main/java/com/doc/framework/web/service/SysLoginService.java

@@ -158,7 +158,7 @@ public class SysLoginService {
         }
 
         SysUser user = userService.selectUserByUserName(username);
-        if (user.getExpand() != null) {
+        if (user != null && user.getExpand() != null) {
             //验证是否允许登录的IP
             if (StringUtils.isNotEmpty(user.getExpand().getLoginIp())) {
                 if (!IpUtils.isMatchedIp(user.getExpand().getLoginIp(), IpUtils.getIpAddr())) {