Dependent Fields Configuration form not loading. Throwing Error: Call to a member function getTargetEntityTypeId() on null in Drupal\\dependent_fields\\Plugin\\EntityReferenceSelection\\ViewsSelection->buildConfigurationForm()

Problem/Motivation

While adding a new dependent field (not while editing existing field), after selecting the Make field dependent using views option, the expected form is not loading and we get

Error message
Oops, something went wrong. Check your browser's developer console for more details. 

In the browser's console, we get this message.

{
  "message": "\nAn AJAX HTTP error occurred.\nHTTP Result Code: 500\nDebugging information follows.\nPath: /admin/structure/types/manage/article/add-field/node/field_xxxx?js=true&_drupal_ajax=1&ajax_page_state%5Btheme%5D=claro&ajax_page_state%5Btheme_token%5D=KkpfwMiChINqUNOw1NTLmd4GpIO42s696NzLm-Y5SDc&ajax_page_state%5Blibraries%5D=eJx1kGFuwzAIhS9kJ2fYSSLs0JSOgIdx1e7089ZYUybtH-99z-iZRNtSqOCcjiFkBtN5tVaAJ4F7dEj1cDfWBByrP5lkC1nF8eENeOR_neiqnMB6yHBgyE53jP3x-8lfCVi3CW7wOPumJTV3lZO9Q76SYBTY8QQMK3qEUhAMJJ9h_wdjTxSV2lu8GPW-Jp3ePhrac7qo7S8ifQKmTwwXQl6XRmPR0P-CXlBgw-VH11Cvap6bj9jQ4TjRPE71R09YMxR8W3eS0CraWPA9T9RvXb8AvxOsww\nStatusText: error\nResponseText: The website encountered an unexpected error. Try again later.Error: Call to a member function getTargetEntityTypeId() on null in Drupal\\dependent_fields\\Plugin\\EntityReferenceSelection\\ViewsSelection->buildConfigurationForm() (line 492 of modules/contrib/dependent_fields/src/Plugin/EntityReferenceSelection/ViewsSelection.php). Drupal\\Core\\Field\\Plugin\\Field\\FieldType\\EntityReferenceItem->fieldSettingsForm(Array, Object) (Line: 188)\nDrupal\\field_ui\\Form\\FieldConfigEditForm->form(Array, Object) (Line: 108)\nDrupal\\Core\\Entity\\EntityForm->buildForm(Array, Object)\ncall_user_func_array(Array, Array) (Line: 554)\nDrupal\\Core\\Form\\FormBuilder->retrieveForm('field_config_edit_form', Object) (Line: 396)\nDrupal\\Core\\Form\\FormBuilder->rebuildForm('field_config_edit_form', Object, Array) (Line: 651)\nDrupal\\Core\\Form\\FormBuilder->processForm('field_config_edit_form', Array, Object) (Line: 347)\nDrupal\\Core\\Form\\FormBuilder->buildForm(Object, Object) (Line: 48)\nDrupal\\Core\\Entity\\EntityFormBuilder->getForm(Object, 'default', Array) (Line: 62)\nDrupal\\field_ui\\Controller\\FieldConfigAddController->fieldConfigAddConfigureForm('node', 'field_xxxx')\ncall_user_func_array(Array, Array) (Line: 123)\nDrupal\\Core\\EventSubscriber\\EarlyRenderingControllerWrapperSubscriber->{closure:Drupal\\Core\\EventSubscriber\\EarlyRenderingControllerWrapperSubscriber::wrapControllerExecutionInRenderContext():121}() (Line: 634)\nDrupal\\Core\\Render\\Renderer::{closure:Drupal\\Core\\Render\\Renderer::executeInRenderContext():634}()\nFiber->start() (Line: 635)\nDrupal\\Core\\Render\\Renderer->executeInRenderContext(Object, Object) (Line: 121)\nDrupal\\Core\\EventSubscriber\\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)\nDrupal\\Core\\EventSubscriber\\EarlyRenderingControllerWrapperSubscriber->{closure:Drupal\\Core\\EventSubscriber\\EarlyRenderingControllerWrapperSubscriber::onController():96}() (Line: 183)\nSymfony\\Component\\HttpKernel\\HttpKernel->handleRaw(Object, 1) (Line: 76)\nSymfony\\Component\\HttpKernel\\HttpKernel->handle(Object, 1, 1) (Line: 53)\nDrupal\\Core\\StackMiddleware\\Session->handle(Object, 1, 1) (Line: 48)\nDrupal\\Core\\StackMiddleware\\KernelPreHandle->handle(Object, 1, 1) (Line: 28)\nDrupal\\Core\\StackMiddleware\\ContentLength->handle(Object, 1, 1) (Line: 32)\nDrupal\\big_pipe\\StackMiddleware\\ContentLength->handle(Object, 1, 1) (Line: 118)\nDrupal\\page_cache\\StackMiddleware\\PageCache->pass(Object, 1, 1) (Line: 92)\nDrupal\\page_cache\\StackMiddleware\\PageCache->handle(Object, 1, 1) (Line: 48)\nDrupal\\Core\\StackMiddleware\\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)\nDrupal\\Core\\StackMiddleware\\NegotiationMiddleware->handle(Object, 1, 1) (Line: 53)\nDrupal\\Core\\StackMiddleware\\AjaxPageState->handle(Object, 1, 1) (Line: 54)\nDrupal\\Core\\StackMiddleware\\StackedHttpKernel->handle(Object, 1, 1) (Line: 745)\nDrupal\\Core\\DrupalKernel->handle(Object) (Line: 19)\n",
  "name": "AjaxError"
}

Steps to reproduce

1. Create an Entity Reference view. The error happens only if there is at least one Entity Reference view.
2. Then go to the content type's Manage Fields tab and add a new Reference field.
3. In the Config form of the new Reference Field, select Make field dependent using views option.
4. The expected form is not loaded and the browser's console shows error.

Proposed resolution

The issue seems to be coming from this line inside buildConfigurationForm function:

  $fields = $this->getBundleEditableFields($field_config->getTargetEntityTypeId(), $field_config->getTargetBundle());

The $field_config is null because the following is returning null.

  $field_config = $this->requestStack->getCurrentRequest()->get('field_config');

So, to fix this, we can use some alternative way of fetching $field_config. Since we are inside a Form, we can do this instead:

  $field_config = $form_state->getFormObject()->getEntity();