Fix editor crash when a file can't be instantiated in scene

[luevano]

Fixes #89093
Possibly introduced by #88829 as this added code to show more information when instantiating a node/resource into the scene. Unsupported files (such as .tres as shown in the issue) crash the editor due to an index out of bounds when trying to get the child of the preview_node (there are no children).

Following video shows the fix based on the MRP uploaded. I don't think this messes with the intended behavior. Let me know if I should check for more cases.

2024-03-03.02-05-42.mp4

[KoBeWi]

While the fix is correct for the crash, the real issue is that the code checks whether drop is valid based on extensions. And Texture2D valid extensions includes tres, which means can_instantiate will be true for any Resource, while it shouldn't.

A better fix would be changing the code to use ResourceLoader::get_resource_type() (or whatever we use to check for resource type) instead of relying on extensions. This can be done in addition to your fix though.

[KoBeWi]

What I said can be done in follow-up. The current change is fine as a safeguard.

[ryevdokimov]

Whoops, I should have considered this scenario when writing the PR that introduces this.

If the fix that KoBeWi suggests is applied I believe that will also resolved this other issue of non-instantiable resources creating a fake "Create Node" history.

2024-03-03.10-01-43.mp4

[luevano]

Whoops, I should have considered this scenario when writing the PR that introduces this.

If the fix that KoBeWi suggests is applied I believe that will also resolved this other issue of non-instantiable resources creating a fake "Create Node" history.
2024-03-03.10-01-43.mp4

This also happens when trying to instantiate a node in itself, the "Create Node" shows:

godot.windows.editor.x86_64_ExxAqtNfbH.mp4

[luevano]

Whoops, I should have considered this scenario when writing the PR that introduces this.

If the fix that KoBeWi suggests is applied I believe that will also resolved this other issue of non-instantiable resources creating a fake "Create Node" history.
2024-03-03.10-01-43.mp4

Actually, on this PR build, it doesn't show the "Create Node" like you mentioned, checked with 4.3-dev4 and it actually crashes, too. What build are you using?; only inception'ed scenes like my last comment show up when applying this fix

[ryevdokimov]

Ah sorry, I was using a build before my commit since what I already had open was just following the logic of KoBeWi statement. I can see now that your build would fix this issue too, and how my comment could be confusing.

[luevano]

Ah sorry, I was using a build before my commit since what I already had open was just following the logic of KoBeWi statement. I can see now that your build would fix this issue too, and how my comment could be confusing.

Hey, no issues at all, just wanted to clarify. I've implemented KoBeWi suggestions in the follow up PR, which handles this issue better. I'll look up about the case I commented to also fix that.

[akien-mga]

Superseded by #89126.