### Godot version

v4.0.beta16.official [518b9e580]

### System information

Windows 10

### Issue description

`RichTextLabel` with `threaded` enabled may crash the game or show the following warning if the node is in another scene:

```
W 0:00:03:0802   test.gd:12 @ load_with_scene(): A Thread object has been re-started without wait_to_finish() having been called on it. Please do so to ensure correct cleanup of the thread.
  <C++ Source>   core/os/thread.cpp:76 @ start()
  <Stack Trace>  test.gd:12 @ load_with_scene()
                 test.gd:6 @ load_items()
                 test.gd:26 @ _on_button_pressed()
```

It may crash the game (without any warning) if it's added directly.

In `v4.0.beta15.official [4fa6edc88]` I was able to reproduce the same warning on my project but I can't reproduce it in the attached MRP. I get a different error and will crash too if the node is added directly:

```
E 0:00:03:0019   remove_from_group: Condition "!E" is true.
  <C++ Source>   scene/main/scene_tree.cpp:157 @ remove_from_group()
```


### Steps to reproduce

Click on the  `Load with scene` or `Load with node` buttons in the attached MRP until it shows a warning/error or crashes. It may take a while.

### Minimal reproduction project

[add_chid_bug_b16.zip](https://github.com/godotengine/godot/files/10521402/add_chid_bug_b16.zip)

FontGlyph chr;
	chr.found = true;
	chr.advance = advance;
	if (shape.validate() && shape.contours.size() > 0) {
		int w = (bounds.r - bounds.l);
		int h = (bounds.t - bounds.b);
		int mw = w + p_rect_margin * 4;
		int mh = h + p_rect_margin * 4;
		ERR_FAIL_COND_V(mw > 4096, FontGlyph());
		ERR_FAIL_COND_V(mh > 4096, FontGlyph());
		FontTexturePosition tex_pos = find_texture_pos_for_glyph(p_data, 4, Image::FORMAT_RGBA8, mw, mh, true);
		ERR_FAIL_COND_V(tex_pos.index < 0, FontGlyph());
		ShelfPackTexture &tex = p_data->textures.write[tex_pos.index];
		edgeColoringSimple(shape, 3.0); 
		msdfgen::Bitmap<float, 4> image(w, h); 
		DistancePixelConversion distancePixelConversion(p_pixel_range);
		msdfgen::Projection projection(msdfgen::Vector2(1.0, 1.0), msdfgen::Vector2(-bounds.l, -bounds.b));
		msdfgen::MSDFGeneratorConfig config(true, msdfgen::ErrorCorrectionConfig());
		MSDFThreadData td;
		td.output = &image;
		td.shape = &shape;
		td.projection = &projection;
		td.distancePixelConversion = &distancePixelConversion;
		WorkerThreadPool::GroupID group_task = WorkerThreadPool::get_singleton()->add_native_group_task(&TextServerAdvanced::_generateMTSDF_threaded, &td, h, -1, true, String("FontServerRasterizeMSDF"));
		WorkerThreadPool::get_singleton()->wait_for_group_task_completion(group_task);
		msdfgen::msdfErrorCorrection(image, shape, projection, p_pixel_range, config);
		{
			uint8_t *wr = tex.imgdata.ptrw();
			for (int i = 0; i < h; i++) {
				for (int j = 0; j < w; j++) {