### 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->clearing = false;
	p_script->tool = parser->is_tool();
	if (!p_script->name.is_empty()) {
		if (ClassDB::class_exists(p_script->name) && ClassDB::is_class_exposed(p_script->name)) {
			_set_error("The class '" + p_script->name + "' shadows a native class", p_class);
			return ERR_ALREADY_EXISTS;
		}
	}
	GDScriptDataType base_type = _gdtype_from_datatype(p_class->base_type, p_script);
	int native_idx = GDScriptLanguage::get_singleton()->get_global_map()[base_type.native_type];
	p_script->native = GDScriptLanguage::get_singleton()->get_global_array()[native_idx];
	ERR_FAIL_COND_V(p_script->native.is_null(), ERR_BUG);
	
	switch (base_type.kind) {
		case GDScriptDataType::NATIVE:
			
			break;
		case GDScriptDataType::GDSCRIPT: {
			Ref<GDScript> base = Ref<GDScript>(base_type.script_type);
			if (base.is_null()) {
				return ERR_COMPILATION_FAILED;
			}
			if (main_script->has_class(base.ptr())) {
				Error err = _populate_class_members(base.ptr(), p_class->base_type.class_type, p_keep_state);
				if (err) {
					return err;
				}
			} else if (!base->is_valid()) {
				Error err = OK;
				Ref<GDScript> base_root = GDScriptCache::get_full_script(base->path, err, p_script->path);