Error saving entries of type single from frontend ajax request

[Anubarak]

Description

Single Entries created in the CP don't have an authorId for whatever reasons. When you are trying to save such a single entry with an $authorId is removed in the beforeSave function

// Section type-specific stuff
if ($section->type == Section::TYPE_SINGLE) {
    $this->authorId = null;
    $this->expiryDate = null;
}

So far no problem, but when you send an ajax request the controller does the following

if ($request->getAcceptsJson()) { 
    ......
    $return['authorUsername'] = $entry->getAuthor()->username; /<--- you'll receive an exception here
}

Steps to reproduce

1. Create a new section of type single in the CP, do something with the entry
2. Try to save the entry via frontend ajax request

Steps to solve

change line 572 in EntriesController to

$return['authorUsername'] = $entry->getAuthor()? $entry->getAuthor()->username : '';

Additional info

• Craft version: Craft CMS 3.0.0-RC17

[brandonkelly]

Fixed for the next Craft 2 and Craft 3 releases. Thanks!