I see what you mean. I'm having the same problem trying to do what you're saying. I found a way around it.
Place this line:
PHP Code:
$errorphrase = standard_error(construct_phrase(fetch_error('searchnoresults'), $vbulletin->GPC['userid']));
Under this
PHP Code:
$vbulletin->input->clean_array_gpc('r', array(
'userid' => TYPE_UINT,
'forumchoice' => TYPE_ARRAY,
'childforums' => TYPE_BOOL,
));
And then use this instead to display the error.
PHP Code:
eval($errorphrase);