### 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_warning(nd, GDScriptWarning::EMPTY_FILE);
	}
#endif
	push_multiline(false); 
	parse_program();
	pop_multiline();
#ifdef DEBUG_ENABLED
	if (multiline_stack.size() > 0) {
		ERR_PRINT("Parser bug: Imbalanced multiline stack.");
	}
#endif
	if (errors.is_empty()) {
		return OK;
	} else {
		return ERR_PARSE_ERROR;
	}
}
GDScriptTokenizer::Token GDScriptParser::advance() {
	lambda_ended = false; 
	if (current.type == GDScriptTokenizer::Token::TK_EOF) {
		ERR_FAIL_COND_V_MSG(current.type == GDScriptTokenizer::Token::TK_EOF, current, "GDScript parser bug: Trying to advance past the end of stream.");
	}
	if (for_completion && !completion_call_stack.is_empty()) {
		if (completion_call.call == nullptr && tokenizer.is_past_cursor()) {
			completion_call = completion_call_stack.back()->get();
			passed_cursor = true;
		}
	}
	previous = current;
	current = tokenizer.scan();