test: empty description now None

Author: Lancetnik

tests/utils/test_artifact.py

@@ -32,7 +32,7 @@ def test_new_artifact_empty_description_if_not_provided(self):
         parts = [Part(root=TextPart(text='Another sample'))]
         name = 'Artifact_No_Desc'
         artifact = new_artifact(parts=parts, name=name)
-        self.assertEqual(artifact.description, '')
+        self.assertEqual(artifact.description, None)
 
     def test_new_text_artifact_creates_single_text_part(self):
         text = 'This is a text artifact.'