### 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
ClassNode *n_class = alloc_node<ClassNode>();
	ClassNode *previous_class = current_class;
	current_class = n_class;
	n_class->outer = previous_class;
	if (consume(GDScriptTokenizer::Token::IDENTIFIER, R"(Expected identifier for the class name after "class".)")) {
		n_class->identifier = parse_identifier();
		if (n_class->outer) {
			String fqcn = n_class->outer->fqcn;
			if (fqcn.is_empty()) {
				fqcn = script_path;
			}
			n_class->fqcn = fqcn + "::" + n_class->identifier->name;
		} else {
			n_class->fqcn = n_class->identifier->name;
		}
	}
	if (match(GDScriptTokenizer::Token::EXTENDS)) {
		parse_extends();
	}
	consume(GDScriptTokenizer::Token::COLON, R"(Expected ":" after class declaration.)");
	bool multiline = match(GDScriptTokenizer::Token::NEWLINE);
	if (multiline && !consume(GDScriptTokenizer::Token::INDENT, R"(Expected indented block after class declaration.)")) {
		current_class = previous_class;
		complete_extents(n_class);
		return n_class;
	}
	if (match(GDScriptTokenizer::Token::EXTENDS)) {
		if (n_class->extends_used) {