Update readers.py in cases where the next record contains Empty list instead of None (#275)

* Update readers.py

* Update readers.py

* Update readers.py

---------

Co-authored-by: Wenjun Si <[email protected]>

Author: rrmina

odps/readers.py

@@ -358,7 +358,7 @@ def __next__(self):
         self._load_columns()
 
         values = self._readline()
-        if values is None:
+        if values is None or len(values) == 0:
             raise StopIteration
 
         if self._filtered_col_idxes: