Fix property

Author: dshabin

src/superannotate/lib/core/usecases/annotations.py

@@ -140,7 +140,7 @@ def annotations_to_upload(self):
     @property
     def missing_annotations(self):
         if not self._missing_annotations:
-            return []
+            self._missing_annotations = []
         return self._missing_annotations
 
     def get_annotation_upload_data(