### 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
ExpressionNode *grouped = parse_expression(false);
	pop_multiline();
	if (grouped == nullptr) {
		push_error(R"(Expected grouping expression.)");
	} else {
		consume(GDScriptTokenizer::Token::PARENTHESIS_CLOSE, R"*(Expected closing ")" after grouping expression.)*");
	}
	return grouped;
}
GDScriptParser::ExpressionNode *GDScriptParser::parse_attribute(ExpressionNode *p_previous_operand, bool p_can_assign) {
	SubscriptNode *attribute = alloc_node<SubscriptNode>();
	reset_extents(attribute, p_previous_operand);
	update_extents(attribute);
	if (for_completion) {
		bool is_builtin = false;
		if (p_previous_operand && p_previous_operand->type == Node::IDENTIFIER) {
			const IdentifierNode *id = static_cast<const IdentifierNode *>(p_previous_operand);
			Variant::Type builtin_type = get_builtin_type(id->name);
			if (builtin_type < Variant::VARIANT_MAX) {
				make_completion_context(COMPLETION_BUILT_IN_TYPE_CONSTANT_OR_STATIC_METHOD, builtin_type, true);
				is_builtin = true;
			}
		}
		if (!is_builtin) {
			make_completion_context(COMPLETION_ATTRIBUTE, attribute, -1, true);
		}