Undefined variable php

Saya ingin membuat edit akun, saat menampilkan username & level pada form tidak maslah(muncul) tetapi saat menampilkan password error <br /><b>Notice</b>: Undefined variable: password in <b>C:\xampp\htdocs\sdi2\user.php</b> on line <b>84</b><br /> berikut ini scriptnya

session_start();
$username = $_SESSION['username'];
$password = $_SESSION['password'];
$level = $_SESSION['level'];
if (isset($_GET['id'])) {
		$id = $_GET['id'];
		$edit = mysqli_query($koneksi,"SELECT * FROM user WHERE id ='$id' ");
		while($fiuh = mysqli_fetch_assoc($edit)){
			$username = $fiuh['username'];
			$password = $fiuh['password'];
			$level = $fiuh['level'];
		}
	}

dan formnya

<form action="user.php" method="POST">
    <div class="form-group">
	<label for="username">Username :</label>
	<input type="text" name="username" class="form-control" value="<?php echo $username; ?>">
    </div>
    <div class="form-group">
	<label for="password">Password :</label>
        <input type="text" name="password" class="form-control" value="<?php echo $password; ?>">
    </div>
    <div class="form-group">
	<label for="level">Level :</label>
	<input type="text" name="level" class="form-control" value="<?php echo $level; ?>">
    </div>
    <input type="submit" name="edit" class="btn btn-primary" value="EDIT">
</form>

Kira-kira bagian mana yang salah ya?