adapted the functionality based on review

atdb/taskdatabase/services/specification/input_validation.py

@@ -88,6 +88,10 @@ def recalculate_size(data):
     Operators or ATDB could have removed files from the inputs json blob.
     If that has happened, the task.size_to_process needs to be recalculated
     """
+    if not data:
+        # tasks without inputs should just return
+        return None
+
     logger.info(f'recalculate_size')
     new_size = sum([e["size"] for e in data])
     return new_size
@@ -116,4 +120,5 @@ def validate_inputs(task):
 
     # --- recalculate sizes ---
     size_to_process = recalculate_size(task.inputs)
+    if size_to_process:
         task.size_to_process = size_to_process
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