fix linting and typechecking

src/pipecat/transports/vonage/client.py

@@ -864,7 +864,8 @@ class VonageClient:
                 except Exception as exc:
                     logger.error(f"Exception in SDK callback task: {exc}")
                 finally:
-                    active_tasks.discard(asyncio.current_task())
+                    if (current := asyncio.current_task()) is not None:
+                        active_tasks.discard(current)
                     queue.task_done()
 
             try:

src/pipecat/transports/vonage/video_connector.py

@@ -25,9 +25,9 @@ from pipecat.transports.base_input import BaseInputTransport
 from pipecat.transports.base_output import BaseOutputTransport
 from pipecat.transports.base_transport import BaseTransport
 from pipecat.transports.vonage.client import (
-    Session,
+    Session,  # type: ignore[attr-defined]
-    Stream,
+    Stream,  # type: ignore[attr-defined]
-    Subscriber,
+    Subscriber,  # type: ignore[attr-defined]
     VonageClient,
     VonageClientListener,
 )