Bug in cookie WP HTTP cookie parsing

[josephscott]

There's a small logic bug in the WP HTTP cookie code that will result in a PHP error. The code does an empty check, which is fine, but doesn't take into account the condition where the variable holds a string of spaces. To fix this I've included a small patch to rtrim() the value first, allowing for the empty check to work for this cases.

I ran into this while tracking down an error for some outbound PuSHPress pings on WordPress.com. It was triggering a PHP fatal error because it resulted in an empty object property trying to be referenced.

[dd32]

(In [13887]) Whitespace only Cookie pairs are not permitted; Skip them. Props josephscott. Fixes #12761