Warning: Undefined array key 1 in Drupal\revision_graph\RevisionGraphStorage->formatBranchName() ... RevisionGraphStorage.php

Problem/Motivation

Warning when creating a new node

Warning: Undefined array key 1 in Drupal\revision_graph\RevisionGraphStorage->formatBranchName() (line 58 of modules/contrib/revision_graph/src/RevisionGraphStorage.php).

Drupal\revision_graph\RevisionGraphStorage->formatBranchName('4', 'en') (Line: 23)
Drupal\revision_graph\RevisionGraphStorage->initGraph(Object) (Line: 28)
revision_graph_entity_insert(Object)
call_user_func_array(Object, Array) (Line: 426)
Drupal\Core\Extension\ModuleHandler->Drupal\Core\Extension\{closure}(Object, 'revision_graph') (Line: 405)
Drupal\Core\Extension\ModuleHandler->invokeAllWith('entity_insert', Object) (Line: 433)
Drupal\Core\Extension\ModuleHandler->invokeAll('entity_insert', Array) (Line: 251)
Drupal\Core\Entity\EntityStorageBase->invokeHook('insert', Object) (Line: 903)
Drupal\Core\Entity\ContentEntityStorageBase->invokeHook('insert', Object) (Line: 598)
Drupal\Core\Entity\EntityStorageBase->doPostSave(Object, ) (Line: 784)
Drupal\Core\Entity\ContentEntityStorageBase->doPostSave(Object, ) (Line: 523)
Drupal\Core\Entity\EntityStorageBase->save(Object) (Line: 802)
Drupal\Core\Entity\Sql\SqlContentEntityStorage->save(Object) (Line: 339)
Drupal\Core\Entity\EntityBase->save() (Line: 270)
Drupal\node\NodeForm->save(Array, Object)
call_user_func_array(Array, Array) (Line: 114)
Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object) (Line: 52)
Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object) (Line: 592)
Drupal\Core\Form\FormBuilder->processForm('node_landing_page_form', Array, Object) (Line: 320)
Drupal\Core\Form\FormBuilder->buildForm(Object, Object) (Line: 73)
Drupal\Core\Controller\FormController->getContentResult(Object, Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 564)
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: 159)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 709)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes