How to resolve this? Correct output is not showing. Warning: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given in C:\xampp\htdocs\sms\admin\upstu.php on line 49

<?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 Standard  </th><td>     </td></tr><tr><th>  Enter Student Name </th><td>  
   </td></tr><tr><td></td><td colspan="2"></td></tr></tbody></table>


<?php
if(isset($_POST['submit']))
{
 	include('../dbcon.php');
 	$standard=$_POST['std'];
 	$name=$_POST['name'];
 	$sql="SELECT * FROM `student` WHERE `standard`='$standard' 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><th>No</th><th>Img</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></td>		<td> <?php echo $data['name']; ?> </td>		<td>  <?php echo $data['rollno']; ?> </td>		<td>  EDIT </td>	</tr></tbody></table>