### Godot version

v4.0.3.stable.official [5222a99f5]
Master [6101240231600c871f5c5473872532c68ea3268c] (confirmed by https://github.com/godotengine/godot/issues/77666#issuecomment-1568952502)

### System information

Window 10

### Issue description

References are not unreferenced at the end of `if` scopes.

### Steps to reproduce

Copy, paste and run the snippet below, check the results:

```gdscript
extends Node


func _ready() -> void:
  var ref := RefCounted.new()
  var ref_count : int

  # OK
  ref_count = ref.get_reference_count()
  print('Expected: 1, Result: %d' % ref_count)

  # OK
  if true:
    var temp := ref
    temp = null

  ref_count = ref.get_reference_count()
  print('Expected: 1, Result: %d' % ref_count)

  # FAIL
  if true:
    var temp := ref

  ref_count = ref.get_reference_count()
  print('Expected: 1, Result: %d' % ref_count)
```

Output example:

```
Expected: 1, Result: 1
Expected: 1, Result: 1
Expected: 1, Result: 2
```

### Minimal reproduction project

N/A
err_line = -1;
	err_column = -1;
	error = "";
	parser = p_parser;
	main_script = p_script;
	const GDScriptParser::ClassNode *root = parser->get_tree();
	source = p_script->get_path();
	
	make_scripts(p_script, root, p_keep_state);
	main_script->_owner = nullptr;
	Error err = _populate_class_members(main_script, parser->get_tree(), p_keep_state);
	if (err) {
		return err;
	}
	err = _compile_class(main_script, root, p_keep_state);
	if (err) {
		return err;
	}
	if (has_static_data && !root->annotated_static_unload) {
		GDScriptCache::add_static_script(p_script);
	}
	return GDScriptCache::finish_compiling(main_script->get_path());
}
String GDScriptCompiler::get_error() const {