Modify your wpb_total_posts
function like bellow:
function wpb_total_posts() {
$total = wp_count_posts()->publish;
if($total == 1){
echo 'We found', "<strong>" . $total . "</strong>", 'job';
}elseif($total > 1){
echo 'We found', "<strong>" . $total . "</strong>", 'jobs';
}else{
echo 'No posts found ';
}
}
Here I’m first checking if total amount of post is 1 or more and handling singular/plural accordingly. Lastly if there is no post then rendering “No post found”