### 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_

GDScriptLanguage::get_singleton()->get_recognized_extensions(r_extensions);
}
Error GDScriptEditorTranslationParserPlugin::parse_file(const String &p_path, Vector<String> *r_ids, Vector<Vector<String>> *r_ids_ctx_plural) {
	
	
	
	
	Error err;
	Ref<Resource> loaded_res = ResourceLoader::load(p_path, "", ResourceFormatLoader::CACHE_MODE_REUSE, &err);
	if (err) {
		ERR_PRINT("Failed to load " + p_path);
		return err;
	}
	ids = r_ids;
	ids_ctx_plural = r_ids_ctx_plural;
	Ref<GDScript> gdscript = loaded_res;
	String source_code = gdscript->get_source_code();
	GDScriptParser parser;
	err = parser.parse(source_code, p_path, false);
	ERR_FAIL_COND_V_MSG(err != OK, err, "Failed to parse GDScript with GDScriptParser.");
	GDScriptAnalyzer analyzer(&parser);
	err = analyzer.analyze();
	ERR_FAIL_COND_V_MSG(err != OK, err, "Failed to analyze GDScript with GDScriptAnalyzer.");
	
	GDScriptParser::ClassNode *c = parser.get_tree();
	_traverse_class(c);
	return OK;
}
bool GDScriptEditorTranslationParserPlugin::_is_constant_string(const GDScriptParser::ExpressionNode *p_expression) {