Fix descriptor initialization

Author: GustavoDCC

challenge_storing_groceries/src/challenge_storing_groceries/manipulate_machine.py

@@ -103,7 +103,7 @@ def __init__(self, robot, source_entity, target_entity, item_classifications, kn
 
         segmented_entities_designator = ds.VariableDesignator([], resolve_type=[ClassificationResult])
 
-        closest_item_designator = ds.VariableDesignator(resolve_type=Entity)
+        closest_item_designator = ds.VariableDesignator([], resolve_type=Entity)
 
         current_blacklist = []