Change drag preview property cause crash when exported in release mode only

[yikescloud]

Godot version:
3.2.3 official(steam version)

OS/device including version:
windows 10 professional

Issue description:
Change drag preview property will cause crash on build version( no crash on debug export or in game engine)

Steps to reproduce:

1. Add a itemlist and give it a preview
2. Change preview text in gui_input(check whether the preview is exist)
3. Run in godot or export debug version, run well
4. Export non-debug version. crash when drag

Use call_deferred cannot fix the crash
Maybe some relation with#36724

Minimal reproduction project:
PreviewCrash.zip

[yikescloud]

Set preview to null when drop data can fix the crash

func drop_data(position, data):
	preview = null
	return

Maybe drop data break the gui_input process and free the preview node just before "if preview != null"

[nmrkr]

The engine takes ownership of whatever control you throw at set_drag_preview. Once the drag is completed, the control is deleted by the engine itself. Your var preview then becomes invalid. So it makes sense that clearing the var mitigates the crash.

[KoBeWi]

Upgrade to 3.2.4 and change your check to if preview or if preview != null, you will get error in debug build. To avoid it properly you should do if is_instance_valid(preview).

Here's a similar recent issue: #46359
Tagging as documentation, #46360 will resolve this.

[yikescloud]

Upgrade to 3.2.4 and change your check to if preview or if preview != null, you will get error in debug build. To avoid it properly you should do if is_instance_valid(preview).

Here's a similar recent issue: #46359
Tagging as documentation, #46360 will resolve this.

That will fix the crash, thanks!