wp_editor may not load utf-8 content

[tomas.k.7]

requirements:
wp_options -> blog_charset = 'UTF-8'

brief problem description:
when you send string containing character \xA0 to wp_editor(), it loads without any content.

technical background:
caused by

$output = htmlspecialchars($output, ENT_NOQUOTES, get_option( 'blog_charset' ) );

in wp-includes/formatting.php at lines 2802 and 2821

one of possible examples how to simulate the the issue:

...
$content = html_entity_decode('A A');
wp_editor($content, ...);
...

result is dependent on php version used, some versions may work correctly...

[tomas.k.7]

​http://3v4l.org/1Eb9V

[miqrogroove]

Duplicate of #20368.