Created by: daming-lu

When we process sentiment analysis data, we provide a pair of words and labels. For example, ([9, 18, 1, 28, 761], 0). But when the review is empty, such as ([], 1), Paddle will crash by throwing an error like:

paddle.fluid.core.EnforceNotMet: enforce begin_idx < end_idx failed, 9069 >= 9069

We should add a try except so that the program can continue running for good data.