Error: Call to undefined function Drupal\soembed\Plugin\Filter\variable_get() in Drupal\soembed\Plugin\Filter\SoEmbedFilter->getContents()

This error is triggered when I try to make a new user (visiting admin/people/create , but I'm sure it could be triggered other ways as well:

Error: Call to undefined function Drupal\soembed\Plugin\Filter\variable_get() in Drupal\soembed\Plugin\Filter\SoEmbedFilter->getContents() (line 128 of /code/web/modules/contrib/soembed/src/Plugin/Filter/SoEmbedFilter.php) #0 /code/web/modules/contrib/soembed/src/Plugin/Filter/SoEmbedFilter.php(88): Drupal\soembed\Plugin\Filter\SoEmbedFilter->getContents(NULL, 'http://17139108...') #1 [internal function]: Drupal\soembed\Plugin\Filter\SoEmbedFilter->embed(Array) #2 /code/web/modules/contrib/soembed/src/Plugin/Filter/SoEmbedFilter.php(38): preg_replace_callback('#()(https?://[^...', Array, Array) #3 /code/web/core/modules/filter/src/Element/ProcessedText.php(112): Drupal\soembed\Plugin\Filter\SoEmbedFilter->process('dogs,<br><br>A ...', '') #4 [internal function]: Drupal\filter\Element\ProcessedText::preRenderText(Array) #5 /code/web/core/lib/Drupal/Core/Render/Renderer.php(378): call_user_func(Array, Array) #6 /code/web/core/lib/Drupal/Core/Render/Renderer.php(195): Drupal\Core\Render\Renderer->doRender(Array, true) #7 /code/web/core/lib/Drupal/Core/Render/Renderer.php(151): Drupal\Core\Render\Renderer->render(Array, true) #8 /code/web/core/lib/Drupal/Core/Render/Renderer.php(582): Drupal\Core\Render\Renderer->Drupal\Core\Render\{closure}() #9 /code/web/core/lib/Drupal/Core/Render/Renderer.php(152): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure)) #10 /code/web/core/modules/filter/filter.module(302): Drupal\Core\Render\Renderer->renderPlain(Array) #11 /code/web/profiles/contrib/social/modules/social_features/social_swiftmail/src/Plugin/Mail/SocialSwiftMailer.php(41): check_markup('dogs,<br><br>A ...', 'full_html') #12 [internal function]: Drupal\social_swiftmail\Plugin\Mail\SocialSwiftMailer->Drupal\social_swiftmail\Plugin\Mail\{closure}('dogs,<br><br>A ...') #13 /code/web/profiles/contrib/social/modules/social_features/social_swiftmail/src/Plugin/Mail/SocialSwiftMailer.php(42): array_map(Object(Closure), Array) #14 /code/web/modules/contrib/swiftmailer/src/Plugin/Mail/SwiftMailer.php(107): Drupal\social_swiftmail\Plugin\Mail\SocialSwiftMailer->massageMessageBody(Array) #15 /code/web/modules/contrib/mailsystem/src/Adapter.php(43): Drupal\swiftmailer\Plugin\Mail\SwiftMailer->format(Array) #16 /code/web/core/lib/Drupal/Core/Mail/MailManager.php(279): Drupal\mailsystem\Adapter->format(Array) #17 /code/web/core/lib/Drupal/Core/Mail/MailManager.php(174): Drupal\Core\Mail\MailManager->doMail('user', 'register_admin_...', 'dog@dogs.com', 'en', Array, 'admin@admin...', true) #18 /code/web/core/lib/Drupal/Core/Render/Renderer.php(582): Drupal\Core\Mail\MailManager->Drupal\Core\Mail\{closure}() #19 /code/web/core/lib/Drupal/Core/Mail/MailManager.php(175): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure)) #20 /code/web/modules/contrib/mailsystem/src/MailsystemManager.php(73): Drupal\Core\Mail\MailManager->mail('user', 'register_admin_...', 'dog@dogs.com', 'en', Array, 'admin@admin...', true) #21 /code/web/core/modules/user/user.module(1235): Drupal\mailsystem\MailsystemManager->mail('user', 'register_admin_...', 'dog@dogs.com', 'en', Array, 'admin@admin...') #22 /code/web/core/modules/user/src/RegisterForm.php(120): _user_mail_notify('register_admin_...', Object(Drupal\user\Entity\User)) #23 [internal function]: Drupal\user\RegisterForm->save(Array, Object(Drupal\Core\Form\FormState)) #24 /code/web/core/lib/Drupal/Core/Form/FormSubmitter.php(111): call_user_func_array(Array, Array) #25 /code/web/core/lib/Drupal/Core/Form/FormSubmitter.php(51): Drupal\Core\Form\FormSubmitter->executeSubmitHandlers(Array, Object(Drupal\Core\Form\FormState)) #26 /code/web/core/lib/Drupal/Core/Form/FormBuilder.php(585): Drupal\Core\Form\FormSubmitter->doSubmitForm(Array, Object(Drupal\Core\Form\FormState)) #27 /code/web/core/lib/Drupal/Core/Form/FormBuilder.php(314): Drupal\Core\Form\FormBuilder->processForm('user_register_f...', Array, Object(Drupal\Core\Form\FormState)) #28 /code/web/core/lib/Drupal/Core/Controller/FormController.php(74): Drupal\Core\Form\FormBuilder->buildForm('user_register_f...', Object(Drupal\Core\Form\FormState)) #29 [internal function]: Drupal\Core\Controller\FormController->getContentResult(Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\RouteMatch)) #30 /code/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array) #31 /code/web/core/lib/Drupal/Core/Render/Renderer.php(582): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() #32 /code/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure)) #33 /code/web/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) #34 [internal function]: Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() #35 /code/vendor/symfony/http-kernel/HttpKernel.php(153): call_user_func_array(Object(Closure), Array) #36 /code/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1) #37 /code/web/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #38 /code/web/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #39 /code/web/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #40 /code/web/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(50): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #41 /code/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #42 /code/web/core/lib/Drupal/Core/DrupalKernel.php(657): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #43 /code/web/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request)) #44 {main}.

patch forthcoming