Rearrange function params in Site Icon API

[obenland]

Having to pass null as the first parameter if a site icon for the current blog is requested is not very elegant. Let's put it at the end, as it's even more likely that a fallback URL will be passed that a blog id.

[DrewAPicture]

I agree that having to pass null as a first parameter is not awesome.

+1 for 33325.diff​.

[azaozz]

33325.diff looks good.

[helen]

We don't use !! anywhere else in PHP in core - we cast to bool, which is more readable anyway. Since we're in here, let's change that as well.

[MikeHansenMe]

#33326 takes care of the !! and is dependent on this ticket.

[helen]

In 33605:

Site icon: Rearrange function parameters to avoid frequently passing empty values.

props obenland.
fixes #33325.

[jorbin]

​https://travis-ci.org/aaronjorbin/develop.wordpress/builds/74978783

Either the tests also need to be updated, or this had an unintended change.

[obenland]

In 33607:

Tests: Update Site Icon tests to account for changes in [33605].

H/t jorbin.

Fixes #33325.