Prefixselect in the selected forum

[DeepSea]

Hello,
I don't know how could I add {$prefixselect} in the selected forum (only where is prefix used or selected fid)
Now I have prefixselect on every forum, but this is superfluous when i dont have any prefix in other forum.

[MrBrechreiz]

Open forumdisplay.php and search for

$prefixselect = build_forum_prefix_select($fid, $tprefix);

change to

$dbresult = $db->query("SELECT *
		FROM ".TABLE_PREFIX."threadprefixes
	");
	$row = $db->num_rows($dbresult);
	if($row)
	{
		$prefixselect = build_forum_prefix_select($fid, $tprefix);
	}