Using "OR" in 'meta_query' negates the "NOT EXISTS" compare.

[hereswhatidid]

When using the "NOT EXISTS" compare within 'meta_query' to look for undefined custom fields if I also add in a secondary 'OR' query, the entire query behaves as if I was just checking for "EXISTS". The following code:

'meta_query' => array(
  'relation' => 'OR',
  array(
    'key' => 'status',
    'compare' => 'NOT EXISTS',
  ),
  array(
    'key' => 'status',
    'value' => 'new',
    'compare' => '=',
  ),
);

will return any post that has a value set for the "status" custom field.

[hereswhatidid]

Duplicate of #23268.