### 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
update_extents(assignment);
	make_completion_context(COMPLETION_ASSIGN, assignment);
#ifdef DEBUG_ENABLED
	bool has_operator = true;
#endif
	switch (previous.type) {
		case GDScriptTokenizer::Token::EQUAL:
			assignment->operation = AssignmentNode::OP_NONE;
			assignment->variant_op = Variant::OP_MAX;
#ifdef DEBUG_ENABLED
			has_operator = false;
#endif
			break;
		case GDScriptTokenizer::Token::PLUS_EQUAL:
			assignment->operation = AssignmentNode::OP_ADDITION;
			assignment->variant_op = Variant::OP_ADD;
			break;
		case GDScriptTokenizer::Token::MINUS_EQUAL:
			assignment->operation = AssignmentNode::OP_SUBTRACTION;
			assignment->variant_op = Variant::OP_SUBTRACT;
			break;
		case GDScriptTokenizer::Token::STAR_EQUAL:
			assignment->operation = AssignmentNode::OP_MULTIPLICATION;
			assignment->variant_op = Variant::OP_MULTIPLY;
			break;
		case GDScriptTokenizer::Token::STAR_STAR_EQUAL:
			assignment->operation = AssignmentNode::OP_POWER;
			assignment->variant_op = Variant::OP_POWER;
			break;
		case GDScriptTokenizer::Token::SLASH_EQUAL: