### Godot version

4.0.beta10

### System information

Windows 11

### Issue description
UPDATE: This problem only occurs when the source code contains inner classes

Before 4.0.Beta9, I could get a GDScript instance by `GDScript.new()` and then set the `source_code` property and then `reload()`, but now it throws an error 
```
USER SCRIPT ERROR: Parse Error: Could not find script "".
   at: GDScript::reload (built-in:1644)
```
In my software, I use the above method when the user modifies the code text, and then read the godot log to implement real-time error checking of the custom user script editor. But now this functionality is completely broken

### Steps to reproduce

1. Create a GDScript instance by `GDScript.new()`
2. set the `source_code` property and then `reload()`

### Minimal reproduction project

N/A
#ifdef TOOLS_ENABLED
	HashMap<StringName, Variant>::ConstIterator E = member_default_values_cache.find(p_property);
	if (E) {
		r_value = E->value;
		return true;
	}
	if (base_cache.is_valid()) {
		return base_cache->get_property_default_value(p_property, r_value);
	}
#endif
	return false;
}
ScriptInstance *GDScript::instance_create(Object *p_this) {
	GDScript *top = this;
	while (top->_base) {
		top = top->_base;
	}
	if (top->native.is_valid()) {
		if (!ClassDB::is_parent_class(p_this->get_class_name(), top->native->get_name())) {
			if (EngineDebugger::is_active()) {
				GDScriptLanguage::get_singleton()->debug_break_parse(_get_debug_path(), 1, "Script inherits from native type '" + String(top->native->get_name()) + "', so it can't be assigned to an object of type: '" + p_this->get_class() + "'");
			}
			ERR_FAIL_V_MSG(nullptr, "Script inherits from native type '" + String(top->native->get_name()) + "', so it can't be assigned to an object of type '" + p_this->get_class() + "'" + ".");
		}
	}
	Callable::CallError unchecked_error;
	return _create_instance(nullptr, 0, p_this, Object::cast_to<RefCounted>(p_this) != nullptr, unchecked_error);
}
PlaceHolderScriptInstance *GDScript::placeholder_instance_create(Object *p_this) {