I have a question because there is a partial error in bow_vect = vector.fit_transform.

bow_vect = vect.fit_transform(df1['review'].tolist())

이 부분에서 ValueError: np.nan is an invalid document, expected byte or unicode string.

There is this error, but is it because of the wrong file designation?

df1 is a csv file containing restaurant review stars and review contents, and review is the part containing review contents.