Fixes Twig to ignore non-path aliases instead of erroring

extensions/twig/ViewRenderer.php

@@ -146,8 +146,10 @@ class ViewRenderer extends BaseViewRenderer
         $loader = new \Twig_Loader_Filesystem(dirname($file));
 
         foreach (Yii::$aliases as $alias => $path) {
+            if (is_dir($path)) {
                 $loader->addPath($path, substr($alias, 1));
             }
+        }
         $this->twig->setLoader($loader);
 
         return $this->twig->render(pathinfo($file, PATHINFO_BASENAME), $params);