### 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
p_script->fully_qualified_name = p_class->fqcn;
	p_script->name = p_class->identifier ? p_class->identifier->name : "";
	HashMap<StringName, Ref<GDScript>> old_subclasses;
	if (p_keep_state) {
		old_subclasses = p_script->subclasses;
	}
	p_script->subclasses.clear();
	for (int i = 0; i < p_class->members.size(); i++) {
		if (p_class->members[i].type != GDScriptParser::ClassNode::Member::CLASS) {
			continue;
		}
		const GDScriptParser::ClassNode *inner_class = p_class->members[i].m_class;
		StringName name = inner_class->identifier->name;
		Ref<GDScript> subclass;
		if (old_subclasses.has(name)) {
			subclass = old_subclasses[name];
		} else {
			subclass = GDScriptLanguage::get_singleton()->get_orphan_subclass(inner_class->fqcn);
		}
		if (subclass.is_null()) {
			subclass.instantiate();
		}
		subclass->_owner = p_script;
		subclass->path = p_script->path;
		p_script->subclasses.insert(name, subclass);
		make_scripts(subclass.ptr(), inner_class, p_keep_state);
	}
}
Error GDScriptCompiler::compile(const GDScriptParser *p_parser, GDScript *p_script, bool p_keep_state) {