Follow link: JS error, JS confirm, and inability to unfollow

[afercia]

On a make post, for example:
​https://make.wordpress.org/core/2017/04/21/proposal-for-weekly-core-javascript-chat/

When I click the "Follow" link below the post I get a JS error:
base.js:149 Uncaught TypeError: Cannot use 'in' operator to search for 'data' in null

then, when I click on any other link to leave the page, I get a JS confirm "stay/leave".

When clicking again on the link to unfollow, same JS error and when I visit again the page later, the link is still set on "Follow".

[ocean90]

Jetpack Subscriptions doesn't provide an API to unsubscribe so you'd have to do that on ​https://subscribe.wordpress.com/.

[obenland]

@pento Is this something you could look at? I was able to reproduce

[pento]

In mu-plugins/pub/jetpack-follow-link-for-o2.php, add this before the final die in handle_following_action().

(I saw you were shuffling these plugins around, so I haven't made the change. Also, I'm AFK from the end of this week.)

// Echo success if this was an AJAX request, otherwise redirect
if ( isset( $_GET['ajax'] ) ) {
        echo '1';
} else {
        wp_safe_redirect( get_permalink( $post_id ) );
}

[obenland]

In 6423:

O2 Follow: Avoid JS errors when following comments.

Props pento.
Fixes #2786.