[Bugfix] send None sentinel on final commit so server properly sends transcription.done (#33963)

Signed-off-by: pjs102793 <pjs102793@naver.com>
Co-authored-by: Nick Hill <nickhill123@gmail.com>

vllm/entrypoints/openai/realtime/connection.py

@@ -48,7 +48,6 @@ class RealtimeConnection:
         self.generation_task: asyncio.Task | None = None
 
         self._is_connected = False
-        self._is_input_finished = False
         self._is_model_validated = False
 
         self._max_audio_filesize_mb = envs.VLLM_MAX_AUDIO_CLIP_FILESIZE_MB
@@ -145,7 +144,7 @@ class RealtimeConnection:
             commit_event = InputAudioBufferCommit(**event)
             # final signals that the audio is finished
             if commit_event.final:
-                self._is_input_finished = True
+                self.audio_queue.put_nowait(None)
             else:
                 await self.start_generation()
         else:
@@ -239,11 +238,6 @@ class RealtimeConnection:
                     # finish because websocket connection was killed
                     break
 
-                if self.audio_queue.empty() and self._is_input_finished:
-                    # finish because client signals that audio input
-                    # is finished
-                    break
-
             usage = UsageInfo(
                 prompt_tokens=prompt_token_ids_len,
                 completion_tokens=completion_tokens_len,