### 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 (crect.has_point(p_click)) {
										for (int j = 0; j < (int)frame->lines.size(); j++) {
											_find_click_in_line(frame, j, rect.position + Vector2(0, frame->lines[j].offset.y), rect.size.x, p_click, &table_click_frame, &table_click_line, &table_click_item, &table_click_char, true, p_meta);
											if (table_click_frame && table_click_item) {
												
												table_range = Vector2i(INT32_MAX, 0);
												for (Item *F : table->subitems) {
													ItemFrame *sub_frame = static_cast<ItemFrame *>(F);
													for (int k = 0; k < (int)sub_frame->lines.size(); k++) {
														table_range.x = MIN(table_range.x, sub_frame->lines[k].char_offset);
														table_range.y = MAX(table_range.y, sub_frame->lines[k].char_offset + sub_frame->lines[k].char_count);
													}
												}
												table_offy = off.y;
												table_hit = true;
											}
										}
									}
								}
								idx++;
							}
						} break;
						default:
							break;
					}
				}
			}
		}
		Rect2 rect = Rect2(p_ofs + off - Vector2(0, TS->shaped_text_get_ascent(rid)) - p_frame->padding.position, TS->shaped_text_get_size(rid) + p_frame->padding.position + p_frame->padding.size);
		if (p_table) {