### Godot version

master ([06ccbfe](https://github.com/godotengine/godot/commit/06ccbfe8eec6e840db3df2360dc2804386f940b8))

### System information

PopOS 22.04

### Issue description

Sometimes the doc page is broken when the engine is closed and then restarted.
Closing the doc and opening it again fixes it.

![2023-05-27_22-15](https://github.com/godotengine/godot/assets/3624853/ed202a55-03e8-420a-bc1c-ccfc7f7cd02a)


### Steps to reproduce

- Open a documentation page for any node
- Restart Godot

### Minimal reproduction project

NA

EDIT : Added the commit hash @Calinou 
clear();
	append_text(p_bbcode);
}
void RichTextLabel::append_text(const String &p_bbcode) {
	_stop_thread();
	MutexLock data_lock(data_mutex);
	int pos = 0;
	List<String> tag_stack;
	int indent_level = 0;
	bool in_bold = false;
	bool in_italics = false;
	bool after_list_open_tag = false;
	bool after_list_close_tag = false;
	set_process_internal(false);
	while (pos <= p_bbcode.length()) {
		int brk_pos = p_bbcode.find("[", pos);
		if (brk_pos < 0) {
			brk_pos = p_bbcode.length();
		}
		String txt = brk_pos > pos ? p_bbcode.substr(pos, brk_pos - pos) : "";
		
		if (after_list_close_tag || after_list_open_tag) {
			txt = txt.trim_prefix("\n");
		}
		if (brk_pos == p_bbcode.length()) {
			
			if (txt.is_empty() && after_list_open_tag) {
				txt = "\n";