`wp-remove-post-lock` Ajax request generates notice in `wp_ajax_wp_remove_post_lock()`

[dlh]

Before [38425], when no #active_post_lock was in the DOM, the POST request from post.js with the wp-remove-post-lock action would not include an active_post_lock key, and wp_ajax_wp_remove_post_lock() would return immediately.

After [38425], when no #active_post_lock is in the DOM, active_post_lock is converted to the string "undefined" when formData is supported (I'm using Chrome 53.0.2785.143).

wp_ajax_wp_remove_post_lock() tries to process that value, leading to Undefined offset: 1 after array_map( 'absint', explode( ':', $_POST['active_post_lock'] ) ).

To replicate, visit post-new.php and refresh the page after it loads.

The attached patch would return before the Ajax request occurs in post.js if data.active_post_lock is undefined.

[adamsilverstein]

@dlh thanks for the patch! This looks reasonable, I tested before and after, verified the error you mentioned and see it is solved by the patch. I am attaching a slightly updated version switching to a Yoda conditional.

[adamsilverstein]

use yoda conditional

[azaozz]

The attached patch would return before the Ajax request occurs in post.js

Right, the first thing wp_ajax_wp_remove_post_lock() does is to return early when either post_ID or active_post_lock is empty. Can do the same in JS and not send the request.

[azaozz]

In 38772:

Editor: do not send the request for releasing the post lock on unload when post_ID or active_post_lock is missing.

Props dlh, adamsilverstein.
Fixes #38271.