Revert commit (close attribute not always present?)

Author: fchollet

keras_preprocessing/image.py

@@ -1732,7 +1732,6 @@ def _get_batches_of_transformed_samples(self, index_array):
  target_size=self.target_size,
  interpolation=self.interpolation)
  x = img_to_array(img, data_format=self.data_format)
- img.close()
  params = self.image_data_generator.get_random_transform(x.shape)
  x = self.image_data_generator.apply_transform(x, params)
  x = self.image_data_generator.standardize(x)