Fix: Ensure consistent audio MIME type in LiveRequestQueue

Author: 9chait9

src/google/adk/agents/live_request_queue.py

@@ -70,6 +70,8 @@ def send_content(self, content: types.Content):
     self._queue.put_nowait(LiveRequest(content=content))
 
   def send_realtime(self, blob: types.Blob):
+    if not blob.mime_type:
+      blob.mime_type = "audio/pcm;rate=16000"
     self._queue.put_nowait(LiveRequest(blob=blob))
 
   def send_activity_start(self):