ช่วยด้วยครับ Warning: mysqli_fetch_assoc() expects parameter 1 to be mysqli_result

<?php include "connect.php"; ?>
<div class="uk-container uk-container-center ">
<?php include "headder.php"; ?>
<br>

	<div class="uk-grid">
	<!-------------------------------------------------_menu_------------------------------------------------------>
		<div class="uk-width-2-10">
			<ul class="uk-tab uk-tab-left" data-uk-tab="{connect:'#menu1'}">
				<li><a href="#">เสือ</a></li>
				<li><a href="#">กางเกง</a></li>
				<li><a href="#">รองเท้า</a></li>
			</ul>
		
		</div>
	<!-------------------------------------------------_2_------------------------------------------------------>
		<div class="uk-width-8-10 ">
		
			<ul id="menu1" class="uk-switcher">
	<!-------------------------------------------------_เสื้อ_------------------------------------------------------>
				<li>
				
				<?php
				$sql = "SELECT * FROM products_shirts";
				$result = mysqli_query($conn,$sql) ;
				?>
				<?php
				while ($row = mysqli_fetch_assoc($result))
                    { 
				?>
								<figure class="uk-overlay uk-overlay-hover uk-panel uk-panel-box">
								<img class="uk-overlay-spin" src="images/<?php echo $row['p_img']; ?>" width="240" height="50" alt="">
								<figcaption class="uk-overlay-panel uk-overlay-slide-top">เสื้อ <?php echo $row['p_name']; ?> ราคา <?php echo $row['p_price']; ?>฿</figcaption>
								</figure>
							
					<?php 
						} 
					?>
						
					
			
				</li>
		<!-------------------------------------------------_จบเสื้อ_------------------------------------------------------>
				<li>Hello again!</li>
				<li>Bazinga!</li>
			</ul>
		</div>
	</div>

</div>
<?php
mysqli_close($conn);
?>
<br>
<?php include "footer.php"; ?>