Change logic for case `isinstance(stix_data, list)``

stix2/datastore/taxii.py

@@ -83,8 +83,7 @@ class TAXIICollectionSink(DataSink):
             # adding list of something - recurse on each
             for obj in stix_data:
                 self.add(obj, version=version)
-            else:
-                return  # If the list is empty just return.
+            return
 
         elif isinstance(stix_data, str):
             # adding json encoded string of STIX content