tensorflow: Calling tf.keras.models.load_model / model.save twice fails

Please see CoLab or Github Gist to see live demo.

Steps to reproduce:

1. Create model,compile and fit
2. Save model
3. Load model and fit
4. Save model
5. Load model

Get error: ValueError: Passing a dictionary input to a Sequential Model which doesn't have FeatureLayer as the first layer is an error.

Expected: Model that was loaded and saved again should be loaded without error.