Major Description
According to the documentation for `KStream#transformValues`, nulls returned from `ValueTransformer#transform` are not forwarded. (see KStream#transformValues)
However, this does not appear to be the case. In `KStreamTransformValuesProcessor#process` the result of the transform is forwarded directly.
@Override public void process(final K key, final V value) { context.forward(key, valueTransformer.transform(key, value)); }