### 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
if (err) {
					_set_error(vformat(R"(Could not compile base class "%s" from "%s": %s)", base->fully_qualified_name, base->path, error_names[err]), nullptr);
					return err;
				}
				if (base_root.is_valid()) {
					base = Ref<GDScript>(base_root->find_class(base->fully_qualified_name));
				}
				if (base.is_null()) {
					_set_error(vformat(R"(Could not find class "%s" in "%s".)", base->fully_qualified_name, base->path), nullptr);
					return ERR_COMPILATION_FAILED;
				}
				ERR_FAIL_COND_V(!base->is_valid() && !base->reloading, ERR_BUG);
			}
			p_script->base = base;
			p_script->_base = base.ptr();
			p_script->member_indices = base->member_indices;
		} break;
		default: {
			_set_error("Parser bug: invalid inheritance.", nullptr);
			return ERR_BUG;
		} break;
	}
	for (int i = 0; i < p_class->members.size(); i++) {
		const GDScriptParser::ClassNode::Member &member = p_class->members[i];
		switch (member.type) {
			case GDScriptParser::ClassNode::Member::VARIABLE: {
				const GDScriptParser::VariableNode *variable = member.variable;
				StringName name = variable->identifier->name;
				GDScript::MemberInfo minfo;
				minfo.index = p_script->member_indices.size();