TypeError: Return value of Symfony\Component\Process\Process::close() must be of the type int, null returned

Problem/Motivation

 	TypeError: Return value of Symfony\Component\Process\Process::close() must be of the type int, null returned in Symfony\Component\Process\Process->close() (line 1476 of /data/disk/o2/static/varbase-9.0.3-9.1.15/vendor/symfony/process/Process.php)

#0 /data/disk/o2/static/varbase-9.0.3-9.1.15/vendor/symfony/process/Process.php(1365): Symfony\Component\Process\Process->close()
#1 /data/disk/o2/static/varbase-9.0.3-9.1.15/vendor/symfony/process/Process.php(367): Symfony\Component\Process\Process->updateStatus()
#2 /data/disk/o2/static/varbase-9.0.3-9.1.15/vendor/symfony/process/Process.php(249): Symfony\Component\Process\Process->start()
#3 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/modules/contrib/imagemagick/src/ImagemagickExecManager.php(335): Symfony\Component\Process\Process->run()
#4 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/modules/contrib/imagemagick/src/ImagemagickExecManager.php(408): Drupal\imagemagick\ImagemagickExecManager->runOsShell()
#5 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/modules/contrib/imagemagick/src/Plugin/ImageToolkit/ImagemagickToolkit.php(327): Drupal\imagemagick\ImagemagickExecManager->getInstalledLocales()
#6 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/modules/system/src/Form/ImageToolkitForm.php(94): Drupal\imagemagick\Plugin\ImageToolkit\ImagemagickToolkit->buildConfigurationForm()
#7 [internal function]: Drupal\system\Form\ImageToolkitForm->buildForm()
#8 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/Form/FormBuilder.php(532): call_user_func_array()
#9 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/Form/FormBuilder.php(278): Drupal\Core\Form\FormBuilder->retrieveForm()
#10 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/Controller/FormController.php(73): Drupal\Core\Form\FormBuilder->buildForm()
#11 [internal function]: Drupal\Core\Controller\FormController->getContentResult()
#12 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array()
#13 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/Render/Renderer.php(573): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#14 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext()
#15 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext()
#16 /data/disk/o2/static/varbase-9.0.3-9.1.15/vendor/symfony/http-kernel/HttpKernel.php(158): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}()
#17 /data/disk/o2/static/varbase-9.0.3-9.1.15/vendor/symfony/http-kernel/HttpKernel.php(80): Symfony\Component\HttpKernel\HttpKernel->handleRaw()
#18 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle()
#19 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle()
#20 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(106): Drupal\Core\StackMiddleware\KernelPreHandle->handle()
#21 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/modules/page_cache/src/StackMiddleware/PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass()
#22 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle()
#23 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(52): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle()
#24 /data/disk/o2/static/varbase-9.0.3-9.1.15/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle()
#25 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/core/lib/Drupal/Core/DrupalKernel.php(706): Stack\StackedHttpKernel->handle()
#26 /data/disk/o2/static/varbase-9.0.3-9.1.15/docroot/index.php(19): Drupal\Core\DrupalKernel->handle()
#27 {main}

Steps to reproduce

When I access admin/config/media/image-toolkit after enabling the module, I get this error.

Drupal 9.1.15

# convert -version
Version: ImageMagick 7.0.11-13 Q16 x86_64 2021-05-16 https://imagemagick.org
Copyright: (C) 1999-2021 ImageMagick Studio LLC
License: https://imagemagick.org/script/license.php
Features: Cipher DPC HDRI OpenMP(4.5)
Delegates (built-in): bzlib djvu fontconfig freetype gvc jbig jng jp2 jpeg lcms lqr lzma openexr png tiff webp x xml zip zlib

Any ideas what might be going one? Thanks!