Use Symfony routing - #36

Description
-----------

Okay this one is a bit strange as we've got only one log in Sentry about this and I was not able to reproduce it myself. So the thing is that `$objFirstPage` in the breadcrumb could _potentially_ return a null value. We do check it when generating the frontend URL on line 88 but we don't for getting the row data.

Error log:

```
Error: Call to a member function row() on null
#36 vendor/contao/core-bundle/src/Resources/contao/modules/ModuleBreadcrumb.php(89): compile
#35 vendor/contao/core-bundle/src/Resources/contao/modules/Module.php(214): generate
#34 vendor/contao/core-bundle/src/Resources/contao/modules/ModuleBreadcrumb.php(48): generate
#33 vendor/contao/core-bundle/src/Resources/contao/library/Contao/Controller.php(326): getFrontendModule
…
```

Commits
-------

ddc9ddb0 Fixed the potential no first page error in breadcrumb

Description
-----------

We encountered an `ErrorException` when the page of external redirect type has an insert tag that returns an empty string.

The problem in fact happens in the `UrlHelper` component of Symfony, but I think we should fix it on our side nevertheless.

Stack trace:

```
ErrorException: Warning: Uninitialized string offset 0
#36 /vendor/symfony/http-foundation/UrlHelper.php(42): Symfony\Component\HttpFoundation\UrlHelper::getAbsoluteUrl
#35 /vendor/contao/core-bundle/src/Routing/Content/StringResolver.php(40): Contao\CoreBundle\Routing\Content\StringResolver::resolve
#34 /vendor/contao/core-bundle/src/Routing/ContentUrlGenerator.php(150): Contao\CoreBundle\Routing\ContentUrlGenerator::resolveContent
#33 /vendor/contao/core-bundle/src/Routing/ContentUrlGenerator.php(161): Contao\CoreBundle\Routing\ContentUrlGenerator::resolveContent
#32 /vendor/contao/core-bundle/src/Routing/ContentUrlGenerator.php(70): Contao\CoreBundle\Routing\ContentUrlGenerator::generate
#31 /vendor/contao/core-bundle/contao/modules/Module.php(349): Contao\Module::renderNavigation
#30 /vendor/contao/core-bundle/contao/modules/Module.php(326): Contao\Module::renderNavigation
#29 /vendor/contao/core-bundle/contao/modules/Module.php(326): Contao\Module::renderNavigation
#28 /vendor/contao/core-bundle/contao/modules/ModuleNavigation.php(82): Contao\ModuleNavigation::compile
#27 /vendor/contao/core-bundle/contao/modules/Module.php(213): Contao\Module::generate
#26 /vendor/contao/core-bundle/contao/modules/ModuleNavigation.php(45): Contao\ModuleNavigation::generate
#25 /vendor/contao/core-bundle/contao/library/Contao/Controller.php(410): Contao\Controller::getFrontendModule
…
#1 /vendor/friendsofsymfony/http-cache/src/SymfonyCache/EventDispatchingHttpCache.php(96): Contao\ManagerBundle\HttpKernel\ContaoCache::handle
#0 /public/index.php(42): null
```

Commits
-------

756336e7 Fix a potential issue if the insert tags return an empty string in th…
0a9330c2 Throw an exception if the insert tag returns an empty value
46de08ef CS + Unit test
89521539 Rename the test method