### 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)

if (it != nullptr) {
				Rect2 rect = TS->shaped_text_get_object_rect(rid, objects[i]);
				
				switch (it->type) {
					case ITEM_IMAGE: {
						ItemImage *img = static_cast<ItemImage *>(it);
						img->image->draw_rect(ci, Rect2(p_ofs + rect.position + off, rect.size), false, img->color);
					} break;
					case ITEM_TABLE: {
						ItemTable *table = static_cast<ItemTable *>(it);
						Color odd_row_bg = theme_cache.table_odd_row_bg;
						Color even_row_bg = theme_cache.table_even_row_bg;
						Color border = theme_cache.table_border;
						int h_separation = theme_cache.table_h_separation;
						int col_count = table->columns.size();
						int row_count = table->rows.size();
						int idx = 0;
						for (Item *E : table->subitems) {
							ItemFrame *frame = static_cast<ItemFrame *>(E);
							int col = idx % col_count;
							int row = idx / col_count;
							if (frame->lines.size() != 0 && row < row_count) {
								Vector2 coff = frame->lines[0].offset;
								if (rtl) {
									coff.x = rect.size.width - table->columns[col].width - coff.x;
								}
								if (row % 2 == 0) {
									draw_rect(Rect2(p_ofs + rect.position + off + coff - frame->padding.position, Size2(table->columns[col].width + h_separation + frame->padding.position.x + frame->padding.size.x, table->rows[row])), (frame->odd_row_bg != Color(0, 0, 0, 0) ? frame->odd_row_bg : odd_row_bg), true);
								} else {
									draw_rect(Rect2(p_ofs + rect.position + off + coff - frame->padding.position, Size2(table->columns[col].width + h_separation + frame->padding.position.x + frame->padding.size.x, table->rows[row])), (frame->even_row_bg != Color(0, 0, 0, 0) ? frame->even_row_bg : even_row_bg), true);