Fix editor inspector crashing when the old object is no longer valid

[aaronfranke]

This fixes a crash when the editor inspector tries to edit a new object when the old object is an invalid instance. See the stack trace below. I ran into this situation when closing the editor with a complex scene open. Since this is editor code that only runs once in awhile, it's not performance critical. I tested that this fix is correct by adding an else statement and confirmed that it reached there.

Dumping the backtrace. Please include this when reporting the bug to the project developer.
[1] 1   libsystem_platform.dylib            0x0000000186977584 _sigtramp + 56
[2] EditorInspector::edit(Object*) (in godot.macos.editor.arm64) + 384
[3] EditorInspector::_notification(int) (in godot.macos.editor.arm64) + 324
[4] EditorInspector::EditorInspector()
[5] Object::_predelete() (in godot.macos.editor.arm64) + 132
[6] Node::_notification(int) (in godot.macos.editor.arm64) + 384
[7] Object::_predelete() (in godot.macos.editor.arm64) + 132
[8] Node::_notification(int) (in godot.macos.editor.arm64) + 384
[9] Object::_predelete() (in godot.macos.editor.arm64) + 132
[10] Node::_notification(int) (in godot.macos.editor.arm64) + 384
[11] Object::_predelete() (in godot.macos.editor.arm64) + 132
[12] Node::_notification(int) (in godot.macos.editor.arm64) + 384
[13] Object::_predelete() (in godot.macos.editor.arm64) + 132
[14] Node::_notification(int) (in godot.macos.editor.arm64) + 384
[15] Panel::Panel()
[16] Object::_predelete() (in godot.macos.editor.arm64) + 132
[17] Node::_notification(int) (in godot.macos.editor.arm64) + 384
[18] Object::_predelete() (in godot.macos.editor.arm64) + 132
[19] Node::_notification(int) (in godot.macos.editor.arm64) + 384
[20] Object::_predelete() (in godot.macos.editor.arm64) + 132
[21] SceneTree::finalize() (in godot.macos.editor.arm64) + 64
[22] OS_MacOS::run() (in godot.macos.editor.arm64) + 408
[23] main (in godot.macos.editor.arm64) + 392
[24] 24  dyld                                0x00000001865be0e0 start + 2360
-- END OF BACKTRACE --

[KoBeWi]

This fixes a crash when the editor inspector tries to edit a new object when the old object is an invalid instance. I ran into this situation when closing the editor with a complex scene open.

Node editing should not happen during editor exit.
Although the new object might've been null in this case. Not sure if unediting editors is necessary.

[aaronfranke]

@KoBeWi This happens when the old object is an invalid instance, regardless of what the new object is.

[KoBeWi]

But it still shouldn't happen during exit. Stack trace with symbols could be useful.

[kitbdev]

• Looks related to Crash on closing Editor #91046
• And Fix EditorInspector crash when exiting #91538 and Close editor with shader text edit open crash the engine #93529 and Don't edit current when changing docks (reverted) #90816 (comment)

It seems some use of EditorInspector doesn't clear its edited object before it gets deleted, but it could be a lot of places.
The object should have had a node_removed signal or should at least be cleared before EditorInspector gets deleted.

Also it's important to have that edit(nullptr) in NOTIFICATION_PREDELETE since there are multiple inspectors and some can be deleted before exiting, so they need to disconnect that signal and clear data.

edit: Finding the root cause may not be easy so this fix looks good to me to prevent the crash.

[KoBeWi]

Did you test if it actually fixes the crash? get_validated_object() still uses the object pointer:

godot/core/variant/variant.cpp

Lines 2152 to 2154 in 97b8ad1

	Object *Variant::get_validated_object() const {
	if (type == OBJECT) {
	return ObjectDB::get_instance(_get_obj().id);

AFAIK the only way to safely validate an object is using ObjectID. It will still crash with raw pointers.

[aaronfranke]

@KoBeWi Yes, I did. It fixes the crash. From the OP:

I tested that this fix is correct by adding an else statement and confirmed that it reached there.

I added else { print_line("test"); } and confirmed that it prints this instead of crashing the editor.

[KoBeWi]

I can't reproduce the crash, but the change does not break anything. If you say it fixes something then fine.

[akien-mga]

Thanks!