fix(loader): updated "speech" field setting

batch.py

@@ -145,14 +145,20 @@ class Batch(GeneratorBasedBuilder):
                 'topics': topics
             }
 
-            if spoken is not None:
+            if spoken is None:
+                item['speech'] = None
+            else:
                 speech_cluster_path = spoken.get(row['path'])
 
-                if speech_cluster_path is not None:
+                if speech_cluster_path is None:
+                    item['speech'] = None
+                else:
                     speech_file_path = os.path.join(speech_cluster_path, f'{row["thread"]}.mp3')
 
                     if os.path.isfile(speech_file_path):
                         item['speech'] = speech_file_path
+                    else:
+                        item['speech'] = None
 
             yield i, item