Other plugin cannot show post title on featured image

Hi,
I use this plugin to add a default featured image and use other plugin to add post title covered on featured image. However post title not work if default featured image automatically applied. How can I fix it?

Not knowing if its helpful but below is part of code from other plugin:

function splitTitle($title) {
    $titles = explode("，", $title); 
    if(count($titles)>1)
        return "{$titles[0]} <br/> {$titles[1]}";
    else
        return $title;
}

// add post title
function testFilter($html){
    global $post;
    return '<div class="feature-parent">' . $html . '<p class="feature-title">' . splitTitle(get_the_title()) . '</p></div>';
}
add_filter( 'post_thumbnail_html', 'testFilter');
//add css

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