fix(core):平台无角色用户导出时异常

modules/i3plus-core-apiservice/src/main/java/cn/estsh/i3plus/core/apiservice/controller/busi/SysUserInfoController.java

@@ -395,7 +395,9 @@ public class SysUserInfoController extends CoreBaseController{
                 for (SysRefUserRole sysRefUserRole : sysRefUserRoleList) {
                     roleName.append(sysRefUserRole.getRoleNameRdd()).append(",");
                 }
-                roleName.setLength(roleName.length() - 1);
+                if (roleName.length() != 0) {
+                    roleName.setLength(roleName.length() - 1);
+                }
 
                 // 封装model
                 userExportModel = new UserExportModel(sysUserMap.get(userInfoItem.getUserId()), userInfoItem);