fix(write): ignore undefined properties

[SoulKa]

Closes #152.

Ignore any properties that are undefined. Note that it's not possible (by design) to ignore undefined in getLengthProperty() since returning 0 would result in destroying the stream.

[mcollina]

Thanks for opening a PR! Can you please add a unit test?

[SoulKa]

I added a unit test that tests the new behavior though the test packet might be a little bigger than it needs to. However, I'm unfamiliar with the test framework and the asynchronous parsing makes it hard to debug.

[mcollina]

lgtm

[SoulKa]

Thanks for picking up this issue so fast! I tested this PR once again using npm link in my actual project and it fixed the original issue (passing undefined correlationData to publishAsync()).

[robertsLando]

@mcollina can you merge and release?