### Godot version

v4.0 rc6

### System information

Windows 10

### Issue description

When using a ViewportTexture from a SubViewport on a TextureRect, it throws errors after running the scene once and then switching scenes in the editor.
![Pasted image 20230227212626](https://user-images.githubusercontent.com/44676282/221680047-984fa03e-33d1-4856-9a7f-1700b28423cf.png)


### Steps to reproduce

Run the canvas-scene once.
Switch to another scene in the editor.
Switch back to the canvas-scene

### Minimal reproduction project

[ViewportTextureError.zip](https://github.com/godotengine/godot/files/10844099/ViewportTextureError.zip)

OS::DateTime dt = OS::get_singleton()->get_datetime();
	uint32_t hash = hash_murmur3_one_32(OS::get_singleton()->get_ticks_usec());
	hash = hash_murmur3_one_32(dt.year, hash);
	hash = hash_murmur3_one_32(dt.month, hash);
	hash = hash_murmur3_one_32(dt.day, hash);
	hash = hash_murmur3_one_32(dt.hour, hash);
	hash = hash_murmur3_one_32(dt.minute, hash);
	hash = hash_murmur3_one_32(dt.second, hash);
	hash = hash_murmur3_one_32(Math::rand(), hash);
	static constexpr uint32_t characters = 5;
	static constexpr uint32_t char_count = ('z' - 'a');
	static constexpr uint32_t base = char_count + ('9' - '0');
	String id;
	for (uint32_t i = 0; i < characters; i++) {
		uint32_t c = hash % base;
		if (c < char_count) {
			id += String::chr('a' + c);
		} else {
			id += String::chr('0' + (c - char_count));
		}
		hash /= base;
	}
	return id;
}
void Resource::set_scene_unique_id(const String &p_id) {
	scene_unique_id = p_id;
}
String Resource::get_scene_unique_id() const {