Fix property of type Node duplication when script is attached to a child node

[warriormaster12]

This is a continuation of a last PR where I seemed to have only partially solved the problem with node duplication as pointed out by one of the comments after the PR got merged.

This PR should hopefully solve the edge case when a script is attached to a child node but the user duplicates that node's parent.

[warriormaster12]

@AThousandShips is it possible to get this cherry-picked for 4.2?

[AThousandShips]

I don't know the area well enough to make that call

[ryevdokimov]

I think this is related to this PR and the previous one, but I believe there is an issue when duplicating nodes that have children that are instances of other scenes added via add_childen() and the owner set to its parent. As far as I can tell nothing seems broken when I duplicate, it's just the console gets flooded with these errors.

Edit: Disregard.

[warriormaster12]

Can you confirm that this doesn’t happen with a version of godot before my PRs?

[ryevdokimov]

Ah whoops, I didn't pay attention enough to git blame, and thought the relevant code was introduced there. Ignore this.

[KoBeWi]

There is some bug where if you duplicate a node and the duplicated node has its properties updated, the original will also have them changed.

aoYq8ZNIt4.mp4

[warriormaster12]

@KoBeWi Try again, value now is deeply duplicated so the bug shouldn't happen.

[akien-mga]

Thanks!