fix: type is wrong issue (#12165)

Signed-off-by: yihong0618 <zouzou0208@gmail.com>

api/services/audio_service.py

@@ -139,7 +139,7 @@ class AudioService:
                     return Response(stream_with_context(response), content_type="audio/mpeg")
                 return response
         else:
-            if not text:
+            if text is None:
                 raise ValueError("Text is required")
             response = invoke_tts(text, app_model, voice)
             if isinstance(response, Generator):