Check for WP_Error earlier in edit_post

[alexdunae]

When working with custom post types where I hadn't assign the edit_others capabilities, _wp_translate_postdata was returning WP_Error.

edit_post checks for WP_Error, but not before assuming that the return value is actually array and triggering an ugly error.

[nacin]

Sure, looks good. Will want to blame the surrounding code to see why that got inserted.

[nacin]

#14334 closed as a duplicate.

[nacin]

(In [16761]) Move [14551] to after the is_wp_error check. see #13133, fixes #15511, props alexdunae.