### 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 
String fnt = tag.substr(5, tag.length()).unquote();
			Ref<Font> fc = ResourceLoader::load(fnt, "Font");
			if (fc.is_valid()) {
				push_font(fc);
			}
			pos = brk_end + 1;
			tag_stack.push_front("font");
		} else if (tag.begins_with("font ")) {
			Vector<String> subtag = tag.substr(2, tag.length()).split(" ");
			_normalize_subtags(subtag);
			Ref<Font> font = theme_cache.normal_font;
			DefaultFont def_font = NORMAL_FONT;
			ItemFont *font_it = _find_font(current);
			if (font_it) {
				if (font_it->font.is_valid()) {
					font = font_it->font;
					def_font = font_it->def_font;
				}
			}
			Ref<FontVariation> fc;
			fc.instantiate();
			int fnt_size = -1;
			for (int i = 1; i < subtag.size(); i++) {
				Vector<String> subtag_a = subtag[i].split("=", true, 1);
				_normalize_subtags(subtag_a);
				if (subtag_a.size() == 2) {
					if (subtag_a[0] == "name" || subtag_a[0] == "n") {
						String fnt = subtag_a[1];
						Ref<Font> font_data = ResourceLoader::load(fnt, "Font");
						if (font_data.is_valid()) {