assign None to time

Author: IsseW

rerun_py/rerun_sdk/rerun/blueprint/api.py

@@ -482,6 +482,8 @@ def __init__(
             self.time = to_nanos(duration_cursor)
         elif timestamp_cursor is not None:
             self.time = to_nanos_since_epoch(timestamp_cursor)
+        else:
+            self.time = None
 
     def _log_to_stream(self, stream: RecordingStream) -> None:
         """Internal method to convert to an archetype and log to the stream."""