### Godot version

4.0 -> latest

**I've tested all this versions:**
4.0, 4.0.1, 4.0.2, 4.0.3, 4.0.4
4.1, 4.1.1
4.2 dev 4

in all this versions problem exists.

### System information

Fedora 38, macOS

### Issue description

I have found a very strange bug while generating translations. The presence of a method modifying the dictionary's content causes the editor to crash during the generation of the translation template.

The mere presence of an uninvoked method causes a crash.

**Edit: The issue occurs not only with singletons. Any script containing a method that modifies any dictionary leads to a crash.**

### Steps to reproduce

**Project -> Project Settings -> Localizations -> Generate POT -> Add (Add your singleton)**

```
extends Node

var session_data = {
	"coins" : 0,
	"power": 0
}

var shop_items = [
	{
		"id": "max_hp",
		"name": tr("First Shop Item"),
		"desc": tr("Great tool."),
	}
]

func add_power(val: int):
	session_data["power"] += val
```

_⚠️ Problem is in add_power method, not in shop_items._


**Project -> Project Settings -> Localizations -> Generate POT -> Generate**

And... Crash.


[Nagranie ekranu z 2023-09-14 13-10-42.webm](https://github.com/godotengine/godot/assets/5132385/6a00805a-34c8-408e-9b00-eb5875301312)



### Minimal reproduction project

[translation_gm_crash.zip](https://github.com/godotengine/godot/files/12104763/translation_gm_crash.zip)

_Just open project and go to: Project -> Project Settings -> Localizations -> Generate POT -> Generate_

assignment_patterns.insert("text");
	assignment_patterns.insert("placeholder_text");
	assignment_patterns.insert("tooltip_text");
	first_arg_patterns.insert("set_text");
	first_arg_patterns.insert("set_tooltip_text");
	first_arg_patterns.insert("set_placeholder");
	first_arg_patterns.insert("add_tab");
	first_arg_patterns.insert("add_check_item");
	first_arg_patterns.insert("add_item");
	first_arg_patterns.insert("add_multistate_item");
	first_arg_patterns.insert("add_radio_check_item");
	first_arg_patterns.insert("add_separator");
	first_arg_patterns.insert("add_submenu_item");
	second_arg_patterns.insert("set_tab_title");
	second_arg_patterns.insert("add_icon_check_item");
	second_arg_patterns.insert("add_icon_item");
	second_arg_patterns.insert("add_icon_radio_check_item");
	second_arg_patterns.insert("set_item_text");
}