Undefine index: session error - php

Question

Whenever someone login $_SESSION['semail']; and $_SESSION['username2'] are set. Whenever I go to profile page then I set session into a variable like $email = $_SESSION['semail'];
Then in error log an error is recorded as:
Undefined index: semail in /home/twekr/public_html/profile.php on line 11
My session start like this at top of page:
session_name('twekr');
session_start();
ob_start();
Here is the small part of script which is creating error:
<?php
session_name('twekr');
session_start();
ob_start();
if(!isset($_SESSION['semail']))
{
header("Location:https://www.twekr.com/");
}
if(isset($_GET['user']))
{
$id = $_GET['user'];
$user = $_SESSION['semail'];
$userid1 = $_SESSION['username2'];
include_once('config/db.php');
include_once('frnds/functions.php');
require('config/dbsettings.php');
$userquery= "SELECT * FROM users WHERE email='$user'";
$userquery=$sp->query($userquery) or die($sp->error);
$info=$userquery->fetch_object();
$userr = $info->username;
This is the small part of login script where I set session:
$_SESSION['username2'] = $get['username'];
$_SESSION['semail'] = $uemail;
$get is performed here below:
$check_login = mysqli_query($con, "SELECT username FROM users WHERE
email ='$uemail' AND password ='$upass'");
if(mysqli_num_rows($check_login) ==1) {
$get = mysqli_fetch_array($check_login);
$_SESSION['username2'] = $get['username'];