InvalidArgumentException: Source path has to start with a slash. in Drupal\Core\Path\AliasManager->getAliasByPath() line 186 of core/lib/Drupal/Core/Path/AliasManager.php

I have updated the Drupal core version 8.5.5 to 8.6.13.
I am trying to access config > System > Basic site settings (admin/config/system/site-information) it is getting the below error.

The website encountered an unexpected error. Please try again later.InvalidArgumentException: Source path has to start with a slash. in Drupal\Core\Path\AliasManager->getAliasByPath() (line 186 of core/lib/Drupal/Core/Path/AliasManager.php).

Drupal\system\Form\SiteInformationForm->buildForm(Array, Object)
call_user_func_array(Array, Array) (Line: 518)
Drupal\Core\Form\FormBuilder->retrieveForm('system_site_information_settings', Object) (Line: 275)
Drupal\Core\Form\FormBuilder->buildForm('system_site_information_settings', Object) (Line: 93)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 582)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 151)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 68)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 119)
Drupal\cdn\StackMiddleware\DuplicateContentPreventionMiddleware->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 693)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Steps to reproduce

1. Clean Drupal installation
2. Go to admin/structure/block, edit any (for example: Search) block that appears on the frontpage
3. Go to pages tab and set /user/* and click "Show for the listed pages"
4. Go to your.site/index.php.php
5. There is an exception: InvalidArgumentException: Source path .php has to start with a slash. in Drupal\Core\Path\AliasManager->getAliasByPath() (line 229 of core/lib/Drupal/Core/Path/AliasManager.php).