Remove spurious assertion

Author: mattyouill

s3filter/op/sql_table_scan.py

@@ -300,7 +300,7 @@ def on_numpy_array(np_array):
                     df = op.fn(df)
 
                 if first_tuple:
-                    assert (len(df.columns.values) > 0)
+                    # assert (len(df.columns.values) > 0)
                     # op.send(TupleMessage(Tuple(df.columns.values)), op.consumers)
                     first_tuple = False