remove_cap can't unset a negative capability

[johnjamesjacoby]

WP_User::add_cap() accepts two parameters -- the second decides if a user does or does not have the capability. I.E.:

$user->add_cap( 'foo', false );

means a user will not have a capability that any role otherwise allows.

WP_User::remove_cap( 'foo' ) incorrectly does an empty() check rather than ! isset(), preventing negative capabilities from being unset from a users individual capabilities array.

This makes it impossible to revert negative capabilities without first making them positive, and then removing them.

See: #9128

They can go in here: ​http://unit-tests.trac.wordpress.org/browser/trunk/tests/user/capabilities.php

In [21940]:

Allow remove_cap() to unset a negative capability. Props johnjamesjacoby. fixes #21786

​[UT1037]