### 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 
Ref<CharFXTransform> charfx = item_custom->char_fx_transform;
					Ref<RichTextEffect> custom_effect = item_custom->custom_effect;
					if (!custom_effect.is_null()) {
						charfx->elapsed_time = item_custom->elapsed_time;
						charfx->range = Vector2i(l.char_offset + glyphs[i].start, l.char_offset + glyphs[i].end);
						charfx->relative_index = l.char_offset + glyphs[i].start - item_fx->char_ofs;
						charfx->visibility = txt_visible;
						charfx->outline = false;
						charfx->font = frid;
						charfx->glyph_index = gl;
						charfx->glyph_flags = gl_fl;
						charfx->glyph_count = gl_cn;
						charfx->offset = fx_offset;
						charfx->color = font_color;
						bool effect_status = custom_effect->_process_effect_impl(charfx);
						custom_fx_ok = effect_status;
						fx_offset += charfx->offset;
						font_color = charfx->color;
						frid = charfx->font;
						gl = charfx->glyph_index;
						txt_visible &= charfx->visibility;
					}
				} else if (item_fx->type == ITEM_SHAKE) {
					ItemShake *item_shake = static_cast<ItemShake *>(item_fx);
					if (!cn) {
						uint64_t char_current_rand = item_shake->offset_random(glyphs[i].start);
						uint64_t char_previous_rand = item_shake->offset_previous_random(glyphs[i].start);
						uint64_t max_rand = 2147483647;
						double current_offset = Math::remap(char_current_rand % max_rand, 0, max_rand, 0.0f, 2.f * (float)Math_PI);
						double previous_offset = Math::remap(char_previous_rand % max_rand, 0, max_rand, 0.0f, 2.f * (float)Math_PI);