[imp] avoid throwing an exception in HasOwner because makes ACL harder

[phproberto]

ACL checks perform a lot of ownership tests. There are some special cases where an owner column may not be present but throwing an error is not the best option.

Example

Creating an item but not assigning the owner column (so it doesn't have owner).

$article = new Article;
$article->bind(['title' => 'Hello World', 'catid' => 1]);

// This will throw an exception
if ($this->canCreate())
{
}

$article = new Article;
$article->bind(['title' => 'Hello World', 'catid' => 1, 'created_by' => 22]);

// This won't throw an exception
if ($this->canCreate())
{
}