[wp-trac] [WordPress Trac] #57469: retrieve_widgets(): fatal error when a sidebar's widgets set to null (array is expected)

[WordPress Trac]

#57469: retrieve_widgets(): fatal error when a sidebar's widgets set to null (array
is expected)
--------------------------+-----------------------
 Reporter:  kesselb       |       Owner:  (none)
     Type:  defect (bug)  |      Status:  reopened
 Priority:  normal        |   Milestone:
Component:  Widgets       |     Version:  4.9
 Severity:  normal        |  Resolution:
 Keywords:  php80 close   |     Focuses:
--------------------------+-----------------------
Changes (by ikriv):

 * status:  closed => reopened
 * resolution:  invalid =>


Comment:

 I was sitting on an old theme for a few years, and I hit this bug. I would
 see a TypeError exception in array_merge() any time I open the 'widgets'
 page, or after I have upgraded to a new theme.

 The problem seems to be corrupted widgets information in the database. An
 investigation showed that $sidebars_widgets array contains a NULL item
 with key 'subsidiary'.
 I.e. it looked like this:

 {{{
 (
     [wp_inactive_widgets] => Array(...)
     [primary] => Array(...)
     [subsidiary] => NULL
 )
 }}}

 Since $sitebars_widgets is a global variable, it is hard to tell who and
 why was adding a NULL element. Anyway, the problem goes away if I add the
 following to retrieve_widgets() in wp-incudes/widgets.php just before the
 call to _wp_remove_unregistered_widgets():

 {{{
         // remove any NULL elements
         $sidebars_widgets = array_filter($sidebars_widgets);
 }}}

 I suggest to reopen this bug and add this filter to the production
 version: corrupted databases happen, and it's an easy precaution.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/57469#comment:11>
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