keras example Variational Autoencoder: model can't be serialized with tf.keras.models.save_model()

[silvererudite]

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During uploading trained model on hugging face as described here https://keras.io/examples/generative/vae/ it says ValueError: Model should be built before trying to save
Link to Colab example with reproducible error: https://colab.research.google.com/drive/15X_vN59lbWXn2PQyAwWDoU6uBYXkdi2v?usp=sharing