### 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
push_error(R"(Cannot use "extends" more than once in the same class.)");
		}
		parse_extends();
		end_statement("superclass");
	}
	parse_class_body(multiline);
	complete_extents(n_class);
	if (multiline) {
		consume(GDScriptTokenizer::Token::DEDENT, R"(Missing unindent at the end of the class body.)");
	}
	current_class = previous_class;
	return n_class;
}
void GDScriptParser::parse_class_name() {
	if (consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected identifier for the global class name after "class_name".)")) {
		current_class->identifier = parse_identifier();
		current_class->fqcn = String(current_class->identifier->name);
	}
	if (match(GDScriptTokenizer::Token::EXTENDS)) {
		
		parse_extends();
		end_statement("superclass");
	} else {
		end_statement("class_name statement");
	}
}
void GDScriptParser::parse_extends() {
	current_class->extends_used = true;
	int chain_index = 0;
	if (match(GDScriptTokenizer::Token::LITERAL)) {