Problem mysqli_fetch_assoc() | is nothing to do with bolean ;)

Question

I am new here, I have a problem with the code below: someone can give me a light?

Code.:

<tbody> 
   <?php
   while($linha = mysqli_fetch_assoc ($resultado))
   {
      echo '<tr>';
      echo '<td>'. $linha['ID'] .'</td>';
      echo '<td>'. $linha['id'] .'</td>';
      echo '<td>'. $linha['id'] .'</td>';
      echo '<td>'. $linha['id'] .'</td>';
      echo '<td>'. $linha['id'] .'</td>';
      echo '<td>'. $linha['id'] .'</td>';
      echo '</tr>'; 
   }    
   mysqli_close ($conexao);     
   ?>
</tbody>

Error.:

Warning: mysqli_fetch_assoc() expects Parameter 1 to be mysqli_result, null Given in /home/u666149583/public_html/bootstrap/driver/listar.php on line 70