consistency in twig methods

The method chill_custom_fields_is_empty take now the fields as first argument, and the customField as second argument, to be consistent with other twig methods.

Tests/Templating/Twig/CustomFieldRenderingTwigTest.php

@@ -102,4 +102,27 @@ class CustomFieldRenderingTwigTest extends KernelTestCase
         $this->assertContains('My tailor is rich', $text,
               "The rendering text should contains the 'test' text");
     }
+    
+    public function testIsEmpty()
+    {
+        $cf = $this->getSimpleCustomFieldText();
+        
+        // value is not empty
+        $fields = array(
+           'test' => "My tailor is rich"
+        );
+        
+        $result = $this->cfRendering->isEmptyValue($fields, $cf);
+        
+        $this->assertFalse($result);
+        
+        // value is empty
+        $fields = array(
+           'text' => ''
+        );
+        
+        $result = $this->cfRendering->isEmptyValue($fields, $cf);
+        
+        $this->assertTrue($result);
+    }
 }