PHP Fatal error: Uncaught Error: Call to a member function fetch_object() on boolean in

function display_zoeken($query)
{
global $db; 
global $uri;
$result = $db->query($query);
$display['thumbnail']='';
$i=0;
$display['thumbnail'] .=' <ul class="search-row" >';
 while($row =  $result->fetch_object())
   {
	$urls = detail($row);

	$img_src = $row->profile_image =='' ? 'img/no_image_'.$row->gender.'.jpg': $uri.'controller/'.$row->profile_image;
	  $display['thumbnail'] .= '<li class="listzoek">
        <div class="search-user">
                    <a href="'.$urls.'" class="thumbnail" > <img src="'.$img_src.'" title="dating met '.$row->profile_name.'" > </a>
     </div>
                <div class="search-content">
                    <div class="left" style="width:170px;">
                        <strong><i class="icon-user"></i> '.$row->profile_name.'</strong>
                    </div>
                    <div class="left">
                        <span>'.$row->age.' jaar, uit '.$row->province.'</span>
                    </div>

                    <div class="span6" style="margin-left:0px; line-height: 21px;">
                       '.substr($row->aboutme,0,350).' .. 
                    </div>
                </div>
                <div class="search-meta">
                    <a href="'.$urls.'" class="btn btn-small btn-info"><i class="icon-camera"></i> Bekijk profiel</a>
                    <a href="'.$urls.'" class="btn btn-small btn-success"><i class="icon-envelope"></i>  Stuur Bericht </a>
                    Test
					<div class="btn btn-small">'.$row->fotos.' foto(s)</div>
                </div>
				</li>';
	  $i++;
   }

if ($i == 0)
$display['thumbnail'] .=' <h3> Geen resultaten gevonden! </h3>';
$display['thumbnail'] .=' </ul>';
return $display;
}

$display['thumbnail'] .=' <ul class="search-row" >';
 while($row =  $result->fetch_object())