### 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 
_stop_thread();
	MutexLock data_lock(data_mutex);
	ItemShake *item = memnew(ItemShake);
	item->strength = p_strength;
	item->rate = p_rate;
	item->connected = p_connected;
	_add_item(item, true);
}
void RichTextLabel::push_wave(float p_frequency = 1.0f, float p_amplitude = 10.0f, bool p_connected = true) {
	_stop_thread();
	MutexLock data_lock(data_mutex);
	ItemWave *item = memnew(ItemWave);
	item->frequency = p_frequency;
	item->amplitude = p_amplitude;
	item->connected = p_connected;
	_add_item(item, true);
}
void RichTextLabel::push_tornado(float p_frequency = 1.0f, float p_radius = 10.0f, bool p_connected = true) {
	_stop_thread();
	MutexLock data_lock(data_mutex);
	ItemTornado *item = memnew(ItemTornado);
	item->frequency = p_frequency;
	item->radius = p_radius;
	item->connected = p_connected;
	_add_item(item, true);
}
void RichTextLabel::push_rainbow(float p_saturation, float p_value, float p_frequency) {