Update app.py

app.py

@@ -133,8 +133,8 @@ def convert_text_to_speech(input_text, source_language, target_language):
             "T2ST",  # Task
             "text",  # Input type
             input_text,  # Input text
-            None,  # Empty string for audio name
-            None,  # Empty string for audio name
+            "",  # Empty string for audio name
+            "",  # Empty string for audio name
             source_language,  # Source language
             target_language,  # Target language
             api_name="/run"  # API name