You need to catch those exceptions using a Facebook Api Exception catch block:
function fetchFriends(){
$sparam = array('method' => 'fql.query',
'query' => $fql,
'callback' => '',
'access_token' => $fbtoken);
try {
$fqlResult = $facebook -> api($sparam);
} catch (FacebookApiException $e) {//catch FB
echo 'There is an issue with the Token';
} catch(Exception $e) {//catch PHP
echo $e->getMessage().' in '.$e->getFile().' on line '.$e->getLine();
}
}