Notice: Trying to get property of non-object in wp-admin/edit-form-advanced.php on line 281

[wpdavis]

The problem seems to arise from the fact that when users are imported their old IDs aren't mapped to their new IDs, so then $last_user = get_userdata($last_id) is trying to look up a user that doesn't exist.

[wpdavis]

Killing this off — was using old version of WP importer.

[duck_]

Note that I was thinking of reintroducing importing _edit_last since it's used by get_the_modified_author. If that happens the ID will indeed have to be mapped to the new local ID to stop this.

[Ludwig C.]

This error does still exist when deleting a user and reasigning the posts to an other user. Not only the post_author in wp_posts should be changed, please update wp_postmeta too.

UPDATE wp_postmeta SET meta_value='NEW-USER-ID' WHERE meta_key='_edit_last';

An other solution would be to check the object in edit-form-advanced.php and display 'unknown user' when it is null.

[duck_]

Replying to Ludwig C.:

This error does still exist when deleting a user and reasigning the posts to an other user. Not only the post_author in wp_posts should be changed, please update wp_postmeta too.

Good point. Attached a patch to include the get_userdata() call in the conditional.

[duck_]

In 24816:

Fix notice and show generic last update message if _edit_last references a nonexistent user.

Fixes #15498.