Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in admin\updatestudent.php on line 55

<?php 
session_start();

if(isset($_SESSION['uid']))
{
echo "";  

}
else
{
header('location: ../login.php');

}
?>
<?php
include('header.php'); 
include('titlehead.php');

?>






<table align="center"><tbody><tr><th>Enter Standerd</th><td>
</td><th>Enter Student Name</th><td></td><td colspan="2"></td></tr></tbody></table>


 
<?php
if(isset($_POST['submit']))
{
include('../dbcon.php');

$standerd = $_POST['standerd'];
$name = $_POST['stuname'];

$sql="SELECT * FROM `studentinfo` WHERE `standerd`='$standerd' AND `name` LIKE `%$name%`  ";
$run=mysqli_query($con,$sql);

if(mysqli_num_rows($run)<1)
{

echo "";
}
else
{
$count=0;
while($data=mysqli_fetch_assoc($run))
{
$count++;
?>  
<?php

}
}


}
?>           

<table align="center" width="80%" border="1" style="margin-top: 10px"><tbody><tr style="background-color: #000; color: #fff"><th>No</th><th>Image</th><th>Name</th><th>ROLL NO</th><th>Edit</th></tr><tr><td colspan="5">No Records Found</td></tr><tr><td><?php echo $count; ?></td><td><img scr="../dataimg/<?php echo $data['image']; ?>" style="max-width:100px;"</td><td><?php echo $data['name']; ?></td><td><?php echo $data['rollno']; ?></td><td>Edit</td></tr></tbody></table>