### 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)

for (int i = 0; i < objects.size(); i++) {
			Item *it = reinterpret_cast<Item *>((uint64_t)objects[i]);
			if (it != nullptr) {
				Rect2 rect = TS->shaped_text_get_object_rect(rid, objects[i]);
				rect.position += p_ofs + off;
				if (p_click.y >= rect.position.y && p_click.y <= rect.position.y + rect.size.y) {
					switch (it->type) {
						case ITEM_TABLE: {
							ItemTable *table = static_cast<ItemTable *>(it);
							int idx = 0;
							int col_count = table->columns.size();
							int row_count = table->rows.size();
							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;
									}
									Rect2 crect = Rect2(rect.position + coff - frame->padding.position, Size2(table->columns[col].width + theme_cache.table_h_separation, table->rows[row] + theme_cache.table_v_separation) + frame->padding.position + frame->padding.size);
									if (col == col_count - 1) {
										if (rtl) {
											crect.size.x = crect.position.x + crect.size.x;
											crect.position.x = 0;
										} else {
											crect.size.x = get_size().x;
										}
									}