Appending array to itself causes crash without any errors

[aomimezura]

Godot version:

3.1

OS/device including version:

Ubuntu 14.04

Issue description:

If you append an array to itself, the game crashes without showing any errors or printing any text before the append is done making debugging the crash extremely difficult.

Steps to reproduce:
Create array. Next, print something. Then append the array to itself. Run. You will see the game crash WITHOUT the print working and you get no error messages.
SelfReferenceBug.zip

Minimal reproduction project:

[Zireael07]

I believe it's a dupe of an existing issue, but I can't find it atm.

[qarmin]

This happens because Variant::operator String call self recursively.

[aomimezura]

I understand WHY it happens, just not why it doesn't tell you it's an error. It was a difficult bug to track down in my code because of it.

[groud]

I understand WHY it happens, just not why it doesn't tell you it's an error.

I think @qarmin's message was not addressed to you specifically, but to anyone who wanted to work on this issue.

But yeah, the engine should raise an error.

[akien-mga]

Related to #1289.