Notice: Undefined property: stdClass::$size in mailchimp_insert_drupal_form_tag()

I had a Mailchimp signup form as a block and a page and everything was running normally. I created a new list on mailchimp, refreshed the lists in Drupal and then created a new signup form as a page and a block. This error comes up when I access the form page or whatever page the block is placed on. The signup form appears to work correctly, I can still add myself to the list, but this error shows up when the page loads. The code below was copied from my log messages. It appears to happen when I add a second signup form in Drupal because I tried creating a signup form with a different list and the same result happened.

When I look at the log after loading a page with two different signup form block on it, the error shows up twice, I thought it was because there were 2 forms on the page but actually there are 3 so I'm not sure why there are only 2 errors. This error only seems to show up when I have 2 signup forms created in the Mailchimp module. When I delete the second form and go back to the page with the block added to it, the error is gone.

Edit: This does happen, at least some of the time. The user is getting subscribed but I have seen the log notification. Not sure why I didn't see it previously
I also noticed that I was not getting a log message notifying me that someone was subscribed to the list. I don't know what is going on to cause that but I assume that this error is somehow causing that notification to not go through. The user still sees the confirmation message as normal but there isn't a log message confirming it.

Here is the location listed in the log message:http://mysite/support_signup?q=support_signup

Notice: Undefined property: stdClass::$size in mailchimp_insert_drupal_form_tag() (line 1236 of /code/modules/mailchimp/mailchimp.module) #0 /code/core/includes/bootstrap.inc(566): _drupal_error_handler_real(8, 'Undefined prope...', '/code/modules/m...', 1236, Array) #1 /code/modules/mailchimp/mailchimp.module(1236): _drupal_error_handler(8, 'Undefined prope...', '/code/modules/m...', 1236, Array) #2 /code/modules/mailchimp/modules/mailchimp_signup/src/Form/MailchimpSignupPageForm.php(124): mailchimp_insert_drupal_form_tag(Object(stdClass)) #3 [internal function]: Drupal\mailchimp_signup\Form\MailchimpSignupPageForm->buildForm(Array, Object(Drupal\Core\Form\FormState)) #4 /code/core/lib/Drupal/Core/Form/FormBuilder.php(514): call_user_func_array(Array, Array) #5 /code/core/lib/Drupal/Core/Form/FormBuilder.php(271): Drupal\Core\Form\FormBuilder->retrieveForm('mailchimp_signu...', Object(Drupal\Core\Form\FormState)) #6 /code/core/lib/Drupal/Core/Form/FormBuilder.php(212): Drupal\Core\Form\FormBuilder->buildForm(Object(Drupal\mailchimp_signup\Form\MailchimpSignupPageForm), Object(Drupal\Core\Form\FormState)) #7 /code/modules/mailchimp/modules/mailchimp_signup/src/Controller/MailchimpSignupController.php(33): Drupal\Core\Form\FormBuilder->getForm(Object(Drupal\mailchimp_signup\Form\MailchimpSignupPageForm)) #8 [internal function]: Drupal\mailchimp_signup\Controller\MailchimpSignupController->page('signup_support') #9 /code/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(123): call_user_func_array(Array, Array) #10 /code/core/lib/Drupal/Core/Render/Renderer.php(576): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() #11 /code/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(124): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure)) #12 /code/core/lib/Drupal/Core/EventSubscriber/EarlyRenderingControllerWrapperSubscriber.php(97): Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) #13 [internal function]: Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() #14 /code/vendor/symfony/http-kernel/HttpKernel.php(153): call_user_func_array(Object(Closure), Array) #15 /code/vendor/symfony/http-kernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1) #16 /code/core/lib/Drupal/Core/StackMiddleware/Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #17 /code/core/lib/Drupal/Core/StackMiddleware/KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #18 /code/core/modules/page_cache/src/StackMiddleware/PageCache.php(99): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #19 /code/core/modules/page_cache/src/StackMiddleware/PageCache.php(78): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true) #20 /code/core/modules/ban/src/BanMiddleware.php(50): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #21 /code/core/lib/Drupal/Core/StackMiddleware/ReverseProxyMiddleware.php(47): Drupal\ban\BanMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #22 /code/core/lib/Drupal/Core/StackMiddleware/NegotiationMiddleware.php(50): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #23 /code/vendor/stack/builder/src/Stack/StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #24 /code/core/lib/Drupal/Core/DrupalKernel.php(657): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true) #25 /code/index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request)) #26 {main}.