ขอวิธีเเก้เกี่ยวกับการขึ้น error mysqli_fetch_array() expects parameter 1 to br mysqlli_result, boolean given

 รบกวนขอวิธีเเก้ไขการขึ้น Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in 
หน่อยครับ

$total = 0;
$pro_id = isset($_GET['pro_id']);
$pro_stock = isset($_GET['pro_stock']);

$sql = "select * from product where pro_id=$pro_id";
$query = mysqli_query($con, $sql);
while ($row = mysqli_fetch_array($query)) {
$sum = $row['pro_price'] * $pro_stock;
$total += $sum;
?>
<tr>
<td align='center'>
<?php echo $i += 1; ?> parameter 1 to be mysqli_result, boolean given in
</td>
<td> <?php echo $row["pro_name"]; ?> </td>
<td align='right'><?php echo number_format($row['pro_price'], 2); ?> </td>
<td align='right'><?php echo $pro_stock; ?></td>
<td align='right'><?php echo number_format($sum, 2); ?></td>
</tr>
<input type="hidden" name="pro_name" value="<?php echo $row['pro_name']; ?>" class="form-control" required placeholder="ชื่อ-สกุล" />
<tr>
<td align='right' colspan='4'><b>รวม</b></td>
<td align='right'><b><?php echo number_format($total, 2); ?> </b> </td>
</tr>
<?php
}
?>