### 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 
ERR_FAIL_COND_V(p_frame == nullptr, p_h);
	ERR_FAIL_COND_V(p_line < 0 || p_line >= (int)p_frame->lines.size(), p_h);
	Line &l = p_frame->lines[p_line];
	MutexLock lock(l.text_buf->get_mutex());
	BitField<TextServer::LineBreakFlag> autowrap_flags = TextServer::BREAK_MANDATORY;
	switch (autowrap_mode) {
		case TextServer::AUTOWRAP_WORD_SMART:
			autowrap_flags = TextServer::BREAK_WORD_BOUND | TextServer::BREAK_ADAPTIVE | TextServer::BREAK_MANDATORY;
			break;
		case TextServer::AUTOWRAP_WORD:
			autowrap_flags = TextServer::BREAK_WORD_BOUND | TextServer::BREAK_MANDATORY;
			break;
		case TextServer::AUTOWRAP_ARBITRARY:
			autowrap_flags = TextServer::BREAK_GRAPHEME_BOUND | TextServer::BREAK_MANDATORY;
			break;
		case TextServer::AUTOWRAP_OFF:
			break;
	}
	autowrap_flags = autowrap_flags | TextServer::BREAK_TRIM_EDGE_SPACES;
	
	l.text_buf->clear();
	l.text_buf->set_break_flags(autowrap_flags);
	l.text_buf->set_justification_flags(_find_jst_flags(l.from));
	l.char_offset = *r_char_offset;
	l.char_count = 0;
	
	l.offset.x = _find_margin(l.from, p_base_font, p_base_font_size);
	l.text_buf->set_width(p_width - l.offset.x);
	l.text_buf->set_alignment(_find_alignment(l.from));