Warning: Illegal string offset PHP Wordpress

Question

I have Illegal String Offset Error

This is my code

function _feature_faq($param) {                
    $html = '';
    $html_wrapper='';
    $row = 1;
    $is_faq=false;
    $feature_faq = $param['feature']; // <---
    if(empty($feature_faq)):
        $feature_faq = 'none';
    endif;