implode() [function.implode]: Invalid arguments passed in

I’m not quite sure what’s the problem.. I’ve used the Optimizer on several sites, but on this last one I got on top of the page:
Warning: implode() [function.implode]: Invalid arguments passed in /home/monadrzg/public_html/wp-content/themes/optimizer/lib/functions/core.php on line 25
From core-functions.php:

19. function optimizer_first_image() {
20. if(is_404()){
21. return;
22. }
23. global $wp_query;
24. if( $wp_query->post_count <1){
25. return;
26. }
27. global $post, $posts;
28. $image_url = ”;
29. ob_start();
30. ob_end_clean();
if(preg_match_all(‘/<img.+src=[\'”]([^\'”]+)[\'”].*>/i’, $post->post_content, $matches)){;
$image_url = $matches [1] [0];
}
return $image_url;
}`

Sadly I didn’t take the .php course :/
And I don’t understand what’s wrong with line 25? Are there anyone who can give me a tips?

The webpage is: https://monaduaas.no

Thank you!