Removed empty queries with nullable relationship.

[besanek]

Situation: An entity with nullable one reference. If you find only one entity that has this property is set to null, it generates the empty query.

Example

$book = new Book;
$book->author = NULL;
$book->title = "The book written by anonym";
$bookRepository->persist($book);

///

$bookRepository->find($book->id);

Generates :

SELECT `file`.* 
FROM `file` 
WHERE `file`.`id` IN (NULL)

[Tharos]

Thank you very much for this report with included solution.

You are right and I've just fixed this issue in develop branch (I've also added test – that's why I didn't simply merge your code).

[Majkl578]

@Tharos: Just a side-note: a more polite solution would be cherry-picking @besanek's commit and editing it so the authorship is retained, additionally if you specify e.g. closes [#5] in commit message, the pull/issue will be automatically closed (and the commit referenced from it). This is how e.g. dg does it when merging some pull requests. :) (Don't take it as an insult, it's just an advice.)

[Tharos]

Thank you for your advice. I didn't know this workflow before and I'll definitely use it next time. :) I'm not experienced in handling pull requests enough. So I really appreciate your effort to teach me how to do that well. :)