Check if predicted instance is removed that it's not referenced

sleap/io/dataset.py

@@ -92,7 +92,7 @@
 LABELS_JSON_FILE_VERSION = "2.0.0"
 
 # For debugging, we can replace missing video files with a "dummy" video
-USE_DUMMY_FOR_MISSING_VIDEOS = os.getenv("SLEAP_USE_DUMMY_VIDEOS", default="")
+USE_DUMMY_FOR_MISSING_VIDEOS = os.getenv("SLEAP_USE_DUMMY_VIDEOS", default=True)
 
 
 @attr.s(auto_attribs=True)
@@ -1441,6 +1441,13 @@ def remove_instance(
         if not in_transaction:
             self._cache.remove_instance(frame, instance)
 
+        # Check that if a `PredictedInstance` is removed, that it is not referenced
+        from_predicted_instances = [inst.from_predicted for inst in frame.instances]
+        if instance in from_predicted_instances:
+            containing_inst_idx: int = from_predicted_instances.index(instance)
+            containing_inst: Instance = frame.instances[containing_inst_idx]
+            containing_inst.from_predicted = None
+
         # Also remove instance from `InstanceGroup` if any
         session = self.get_session(frame.video)
         if session is None: