### 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 
return line.get_height(theme_cache.line_separation);
}
void RichTextLabel::_update_theme_item_cache() {
	Control::_update_theme_item_cache();
	theme_cache.normal_style = get_theme_stylebox(SNAME("normal"));
	theme_cache.focus_style = get_theme_stylebox(SNAME("focus"));
	theme_cache.progress_bg_style = get_theme_stylebox(SNAME("background"), SNAME("ProgressBar"));
	theme_cache.progress_fg_style = get_theme_stylebox(SNAME("fill"), SNAME("ProgressBar"));
	theme_cache.line_separation = get_theme_constant(SNAME("line_separation"));
	theme_cache.normal_font = get_theme_font(SNAME("normal_font"));
	theme_cache.normal_font_size = get_theme_font_size(SNAME("normal_font_size"));
	theme_cache.default_color = get_theme_color(SNAME("default_color"));
	theme_cache.font_selected_color = get_theme_color(SNAME("font_selected_color"));
	use_selected_font_color = theme_cache.font_selected_color != Color(0, 0, 0, 0);
	theme_cache.selection_color = get_theme_color(SNAME("selection_color"));
	theme_cache.font_outline_color = get_theme_color(SNAME("font_outline_color"));
	theme_cache.font_shadow_color = get_theme_color(SNAME("font_shadow_color"));
	theme_cache.shadow_outline_size = get_theme_constant(SNAME("shadow_outline_size"));
	theme_cache.shadow_offset_x = get_theme_constant(SNAME("shadow_offset_x"));
	theme_cache.shadow_offset_y = get_theme_constant(SNAME("shadow_offset_y"));
	theme_cache.outline_size = get_theme_constant(SNAME("outline_size"));
	theme_cache.bold_font = get_theme_font(SNAME("bold_font"));
	theme_cache.bold_font_size = get_theme_font_size(SNAME("bold_font_size"));
	theme_cache.bold_italics_font = get_theme_font(SNAME("bold_italics_font"));
	theme_cache.bold_italics_font_size = get_theme_font_size(SNAME("bold_italics_font_size"));
	theme_cache.italics_font = get_theme_font(SNAME("italics_font"));
	theme_cache.italics_font_size = get_theme_font_size(SNAME("italics_font_size"));
	theme_cache.mono_font = get_theme_font(SNAME("mono_font"));
	theme_cache.mono_font_size = get_theme_font_size(SNAME("mono_font_size"));