### Godot version

v4.1.stable.official [970459615]

### System information

Godot v4.1.stable - Windows 10.0.22621 - Vulkan (Forward+) - dedicated NVIDIA GeForce MX330 (NVIDIA; 30.0.15.1169) - 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz (8 Threads)

### Issue description

Calling `RichTextLabel`'s `select_all` method has no visual indicator, but it must have one. 

### Steps to reproduce

- Add `RichTextLabel` node
- Set `selection_enabled` value to be `true`
- Call `$RichTextLabel.select_all() `method in `_ready`

### Minimal reproduction project

[RichTextLabel_bug.zip](https://github.com/godotengine/godot/files/12098913/RichTextLabel_bug.zip)

_validate_line_caches();
	int to_line = main->first_invalid_line.load();
	for (int i = 0; i < to_line; i++) {
		int char_offset = main->lines[i].char_offset;
		if (char_offset <= p_char && p_char < char_offset + main->lines[i].char_count) {
			return i;
		}
	}
	return -1;
}
int RichTextLabel::get_total_character_count() const {
	// 
	int tc = 0;
	Item *it = main;
	while (it) {
		if (it->type == ITEM_TEXT) {
			ItemText *t = static_cast<ItemText *>(it);
			tc += t->text.length();
		} else if (it->type == ITEM_NEWLINE) {
			tc++;
		} else if (it->type == ITEM_IMAGE) {
			tc++;
		}
		it = _get_next_item(it, true);
	}
	return tc;
}
int RichTextLabel::get_total_glyph_count() const {