### 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
AssertNode *assert = alloc_node<AssertNode>();
	push_multiline(true);
	consume(GDScriptTokenizer::Token::PARENTHESIS_OPEN, R"(Expected "(" after "assert".)");
	assert->condition = parse_expression(false);
	if (assert->condition == nullptr) {
		push_error("Expected expression to assert.");
		pop_multiline();
		complete_extents(assert);
		return nullptr;
	}
	if (match(GDScriptTokenizer::Token::COMMA) && !check(GDScriptTokenizer::Token::PARENTHESIS_CLOSE)) {
		assert->message = parse_expression(false);
		if (assert->message == nullptr) {
			push_error(R"(Expected error message for assert after ",".)");
			pop_multiline();
			complete_extents(assert);
			return nullptr;
		}
		match(GDScriptTokenizer::Token::COMMA);
	}
	pop_multiline();
	consume(GDScriptTokenizer::Token::PARENTHESIS_CLOSE, R"*(Expected ")" after assert expression.)*");
	complete_extents(assert);
	end_statement(R"("assert")");
	return assert;
}
GDScriptParser::BreakNode *GDScriptParser::parse_break() {