Update livekit-rtc/livekit/rtc/audio_frame.py

Co-authored-by: Théo Monnom <theo.8bits@gmail.com>

Author: 1egoman

livekit-rtc/livekit/rtc/audio_frame.py

@@ -33,7 +33,7 @@ def __init__(
         sample_rate: int,
         num_channels: int,
         samples_per_channel: int,
-        userdata: dict[str, Any] = {},
+        userdata: dict[str, Any] | None = None,
     ) -> None:
         """
         Initialize an AudioFrame instance.