Handle mapping without mappedBy

[VincentLanglet]

Subject

I am targeting this branch, because BC.

Fix #6219 (comment).

Changelog

### Fixed
- ObjectManipulator::setObject does not throw an error anymore for DoctrineODM Embedded collections.

[greg0ire]

Please summarize the linked issue in the body of your commit message. We should be able to understand what this is about just by reading the git log.

[VincentLanglet]

Please summarize the linked issue in the body of your commit message. We should be able to understand what this is about just by reading the git log.

Please enjoy my first commit with a body @greg0ire 😅

[greg0ire]

Please enjoy my first commit with a body @greg0ire 😅

I am so proud of you!

[greg0ire]

Oh, it's just a link… a summary would really be better IMO. I'm going to read the comment, then read the PR and try to really understand this, and then I will write the summary.

[greg0ire]

Things I changed in the commit message:

1. the commit message subject is about the what. If you read it, then look at the changes, you should think "Indeed, that's what is being done here, not more, not less."
2. the former commit message subject has been moved in the body, because it is about the why. I added an example so that it's less vague, and I kept the link so that people that want to see the discussion can.

[VincentLanglet]

Things I changed in the commit message:

1. the commit message subject is about the what. If you read it, then look at the changes, you should think "Indeed, that's what is being done here, not more, not less."
2. the former commit message subject has been moved in the body, because it is about the why. I added an example so that it's less vague, and I kept the link so that people that want to see the discussion can.

Interesting.
I always tried to write the why in the commit.

If I add a null !== $foo check, I would have create a commit

Avoid error when $foo is null

Rather than, the captain obvious commit

Add null check

But I think I understand your point of view.
You want the what to find your commit in the history, then the why you understand the reason of the commit.

[jordisala1991]

Thank you @VincentLanglet

[greg0ire]

Avoid error when $foo is null

Yeah, and that would be a bit terse… I mean when can $foo be null? It's probably not super obvious since it was missed before, so it might deserve a sentence explaining how this can happen. Hard to do under 50 chars.