Измените

 

Warning: imagepng(/var/www/mojaopstina.rs/www-root/public/images/captcha/0545135729b6ed7755e9e02a1ba8541a.png): failed to open stream: Permission denied in /var/www/mojaopstina.rs/www-root/library/Zend/Captcha/Image.php on line 563