Pdf: Restore previous state after rendering content

In case an exception occurs its output was previously merged
with the rendered content or even PDF..

library/Icinga/File/Pdf.php

@@ -51,14 +51,19 @@ class Pdf
         Environment::raiseExecutionTime(300);
 
         $viewRenderer = $controller->getHelper('viewRenderer');
-        $controller->render(
-            $viewRenderer->getScriptAction(),
-            $viewRenderer->getResponseSegment(),
-            $viewRenderer->getNoController()
-        );
-        $layout = $controller->getHelper('layout')->setLayout('pdf');
+        $viewRenderer->postDispatch();
+
+        $layoutHelper = $controller->getHelper('layout');
+        $oldLayout = $layoutHelper->getLayout();
+        $layout = $layoutHelper->setLayout('pdf');
+
         $layout->content = $controller->getResponse();
         $html = $layout->render();
+
+        // Restore previous layout and reset content, to properly show errors
+        $controller->getResponse()->clearBody($viewRenderer->getResponseSegment());
+        $layoutHelper->setLayout($oldLayout);
+
         $imgDir = Url::fromPath('img');
         $html = preg_replace(
             '~src="' . $imgDir . '/~',

library/Icinga/Web/Controller/ActionController.php

@@ -484,8 +484,8 @@ class ActionController extends Zend_Controller_Action
         }
 
         if ($req->getParam('format') === 'pdf') {
-            $this->shutdownSession();
             $this->sendAsPdf();
+            $this->shutdownSession();
             exit;
         }