Chrome: Fix post visbility when saving a post

[youknowriad]

Posts with a "public" status and a empty string password were being considered "protected" while posts with "public" status and a null or undefined password were being considered "private". This distinction was necessary to allow us to check "password protected" visibility and display an empty password at the same time.

The problem with this is that saving a post automatically fills the password with an empty string which was being considered as password protected.

This fixes the issue by considering all nullable values for the password as "public" posts and introduce a local state in the visibility selector to display the password input even if the password is empty.

[jasmussen]

Not entirely sure how to test. But I tried setting the post as password protected with an empty password and saving. So long as the password field is empty, the indicator still shows "Public", which I suppose is to be expected. The indicator isn't reset back to "public", though, the radio button still shows "public" as selected:

Upon a page reload, this resets to public, though:

Both of which I think are probably fine.

Incidentally, the 405 not allowed error is showing up for me on updating a saved post. I can save posts just fine, I just can't update them:

I don't think that's a regression in this branch, but I think I told @nylen earlier that I could save and update posts. I could probably always save, but never update posts.

[youknowriad]

You're right I forgot to mention that on master, when you save a post, the visibility switches to "password protected" right now and that's what this PR is fixing.

And yes, the behaviour you're seeing is the expected one. The visibility will show "Password Protected" only if you fill the password but the selector allows you to select the "password" radio input to start filling the password (even if the password is empty at first).

[jasmussen]

Sounds good, then 👍 from me.

[aduth]

The logic described in the original pull request text is screaming for tests 😄 (#641)