5.x: fix type error if no sort is set for variables tab

[LordSimal]

This error happens with the current beta state of cakephp/app:5.0.0-beta1 when trying to open the Variables tab on the default homepage.

2022-12-20 18:55:33 error: [TypeError] DebugKit\View\Helper\ToolbarHelper::setSort(): Argument #1 ($sort) must be of type bool, null given, called in <my-app-path>/vendor/cakephp/debug_kit/templates/element/variables_panel.php on line 65 in <my-app-path>/vendor/cakephp/debug_kit/src/View/Helper/ToolbarHelper.php on line 55
Stack Trace:
- <my-app-path>/vendor/cakephp/debug_kit/templates/element/variables_panel.php:65
- <my-app-path>/vendor/cakephp/cakephp/src/View/View.php:1185
- <my-app-path>/vendor/cakephp/cakephp/src/View/View.php:1142
- <my-app-path>/vendor/cakephp/cakephp/src/View/View.php:1689
- <my-app-path>/vendor/cakephp/cakephp/src/View/View.php:673
- <my-app-path>/vendor/cakephp/debug_kit/templates/Panels/view.php:9
- <my-app-path>/vendor/cakephp/cakephp/src/View/View.php:1185
- <my-app-path>/vendor/cakephp/cakephp/src/View/View.php:1142
- <my-app-path>/vendor/cakephp/cakephp/src/View/View.php:782
- <my-app-path>/vendor/cakephp/cakephp/src/Controller/Controller.php:690
- <my-app-path>/vendor/cakephp/cakephp/src/Controller/Controller.php:494
- <my-app-path>/vendor/cakephp/cakephp/src/Controller/ControllerFactory.php:139
- <my-app-path>/vendor/cakephp/cakephp/src/Controller/ControllerFactory.php:114
- <my-app-path>/vendor/cakephp/cakephp/src/Http/BaseApplication.php:329
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Runner.php:77
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Middleware/CsrfProtectionMiddleware.php:168
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Runner.php:73
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Middleware/BodyParserMiddleware.php:157
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Runner.php:73
- <my-app-path>/vendor/cakephp/cakephp/src/Routing/Middleware/RoutingMiddleware.php:116
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Runner.php:73
- <my-app-path>/vendor/cakephp/cakephp/src/Routing/Middleware/AssetMiddleware.php:68
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Runner.php:73
- <my-app-path>/vendor/cakephp/cakephp/src/Error/Middleware/ErrorHandlerMiddleware.php:100
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Runner.php:73
- <my-app-path>/vendor/cakephp/debug_kit/src/Middleware/DebugKitMiddleware.php:60
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Runner.php:73
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Runner.php:58
- <my-app-path>/vendor/cakephp/cakephp/src/Http/Server.php:89
- <my-app-path>/webroot/index.php:37
- [main]:

Request URL: /debug-kit/panels/view/cd48819b-2a38-4e68-aeb5-320fc83bbab7
Referer URL: http://localhost:8765/debug-kit/toolbar/b9175884-57d1-4cb0-bab1-cb06be23a650

we could of course set the default value for setSort(bool $sort = false) as well.

[LordSimal]

I can rebase this after we get #901 merged so the tests are green again.