[chill entity render] fix usage of default entity rendering

Templating/Entity/ChillEntityRender.php

@@ -33,7 +33,7 @@ class ChillEntityRender extends AbstractChillEntityRender
 
     public function renderString($entity, array $options): string
     {
-        return $entity;
+        return (string) $entity;
     }
 
     public function supports($entity, array $options): bool

Templating/Entity/ChillEntityRenderExtension.php

@@ -41,6 +41,11 @@ class ChillEntityRenderExtension extends AbstractExtension
      */
     protected $defaultRender;
     
+    public function __construct()
+    {
+        $this->defaultRender = new ChillEntityRender();
+    }
+    
     public function getFilters()
     {
         return [
@@ -55,12 +60,20 @@ class ChillEntityRenderExtension extends AbstractExtension
     
     public function renderString($entity, array $options = []): string
     {
+        if (NULL === $entity) {
+            return '';
+        }
+        
         return $this->getRender($entity, $options)
             ->renderString($entity, $options);
     }
     
     public function renderBox($entity, array $options = []): string
     {
+        if (NULL === $entity) {
+            return '';
+        }
+        
         return $this->getRender($entity, $options)
             ->renderBox($entity, $options);
     }