Prefilled textarea by custom post content by default

I want textarea to be prefilled with some custom content of custom post type. The following code works well when page loads for first time.

function add_post_id_origin ( $tag, $unused ) {
if ($tag[‘name’] != ‘msg_to_friend’ )
return $tag;

if($tag[‘name’] == ‘msg_to_friend’){

$src = wp_get_attachment_image_src(get_post_thumbnail_id(get_the_ID()), array(100, 100));

$msg .= ‘<p style=”float:left; margin: 0 10px 10px 0;”><img src=”‘.$src[0].'” width=”100px” height=”100px” /></p>’;

$pst = get_post(get_the_ID());

$content = $pst->post_content;
$content = apply_filters(‘the_content’, $content);
$content = str_replace(‘]]>’, ‘]]>’, $content);

$msg .= ‘<p>’ . wp_trim_words($content, 100, ‘…’); ‘</p>’;

$tag[‘values’] = array($msg);
$tag[‘options’] = array(‘readonly’);
}

return $tag;
}

add_filter( ‘wpcf7_form_tag’, ‘add_post_id_origin’, 10, 2);

Problem comes when we click on submit button. It throws a warning of “Trying to get property of non-object in …” in Ajax response. The reason behind the code is that this filter wpcf7_form_tag is called again when we click on submit button and get_the_ID() returns NULL this causes $pst->post_content to throws the warning.

Is there any other way to do this?

https://wordpress.org/plugins/contact-form-7/