Failed to load resource

/administrator/index.php?option=com_invoices&controller=invoice&task=send_email&cid[]=25&ajax=1&type=1&_=1520066605777 Failed to load resource: the server responded with a status of 500 ()

function sendMail(){
        $data = $this->getData();
        
        $params = JComponentHelper::getParams( 'com_invoices' );
        
        $from = $params->get('email_email') ;
        $from_name = $params->get('email_name') ;
        $subject = $params->get('email_subject') ;

        if($data->type == 2){//quote
            $subject = $params->get('email_subject_quote') ;
        }
        
        $subject = str_replace("{invoice_num}", $data->invoice_num, $subject) ;

        $view        = $this->getInvoiceView();
        
        $view->invoice        = $data;
        $view->template        = $this->getTemplate();
        $view->items        = $this->getItems();
        $view->taxes        = $this->getTaxes();
        $view->payments        = $this->getPayments();
        $view->payments2        = $this->getPayments2();
        $view->params        = $params;

        if($view->template->content_email) $view->template->content = $view->template->content_email ;
        
        $view->_path['template'][1] = JPATH_SITE.DS.'components'.DS.'com_invoices'.DS.'views'.DS.'invoice'.DS.'tmpl' ;
        
        $plantilla = 'email' ;
        
        $message = $view->loadTemplate( $plantilla );
        
        $styles = "<style>".$view->template->styles."</style>" ;
        $message = $styles . $message ;
        
        $to = $data->to_email;

        $toBlock = str_replace(" ", "", $to); //Delete spaces between emails
        $toMails = explode(",", $toBlock);

        $mail = JFactory::getMailer();
        $mail->addRecipient($toMails);
        $mail->setsender(array($from, $from_name));
        $mail->setSubject($subject);
        $mail->setbody($message);
        $mail->isHTML(true);

        if($params->get('pdfemail') && InvoicesHelper::PDFavailable()){
            //create PDF
            $viewpdf        = $this->getInvoiceView('dompdf');
            
            $viewpdf->invoice        = $view->invoice    ;
            $viewpdf->template        = $this->getTemplate();
            $viewpdf->items            = $view->items    ;
            $viewpdf->taxes            = $view->taxes    ;
            $viewpdf->payments        = $view->payments;
            $viewpdf->payments2        = $view->payments2;
            $viewpdf->params        = $params;

            if($viewpdf->template->content_pdf) $viewpdf->template->content = $viewpdf->template->content_pdf ;

            $viewpdf->_path['template'][1] = JPATH_SITE.DS.'components'.DS.'com_invoices'.DS.'views'.DS.'invoice'.DS.'tmpl' ;

            if($viewpdf->invoice->invoice_num) $pdfname = $viewpdf->invoice->invoice_num;
            else $pdfname = rand();
            
            $location = JPATH_SITE.DS.$params->get('pdffolder','pdfinvoices').DS.$pdfname . ".pdf" ;

            $pdf = $viewpdf->storepdf($location);

            if($pdf) $mail->addAttachment($location, $viewpdf->invoice->invoice_num . ".pdf") ; 

        }

        $sent = $mail->Send();
        if($sent && $to){
            InvoicesHelper::updateSentDate($data->id);

            //trigger event
            $import = JPluginHelper::importPlugin( 'invoices' );
            $dispatcher = JDispatcher::getInstance();
            $dispatcher->trigger( 'onAfterSendInvoice', array( $data ) );
        }
        return $sent ;
        
    }