Illegal offset type in empty() when editing a draft post by another user

[duck_]

Warning: Illegal offset type in isset or empty in wp-includes/capabilities.php on line 885

Triggered by a call to current_user_can() when building the View Post button for the tool bar.

current_user_can( 'read_post', $post_id ) will return an array containing arrays since [21046] for draft posts created by other users because map_meta_cap() returns an array and its result is being put in an array.

Looks good.

In [21060]:

Fix warning when processing read_post cap. Props duck_. fixes #20917

In [21088]:

Fix warning when processing read_post cap. Props duck_. fixes #20917 for the 3.3 branch.