Make sure that user data is always array to prevent fatal error

When user send bulk messages for example to all group members in a group, the message does not deliver. Furthermore, we do not receive any form of error notification or feedback regarding the delivery failure.

After an investigation has been discovered that during this activity it generates the following error:

TypeError: array_map(): Argument #2 ($array) must be of type array, bool given in /app/html/modules/contrib/social_pwa/src/WebPushManager.php on line 71 #0 /app/html/modules/contrib/social_pwa/src/WebPushManager.php(71): array_map(Object(Closure), false)
#1 /app/html/modules/contrib/social_pwa/modules/activity_send_push/src/Plugin/ActivitySend/PushActivitySend.php(98): Drupal\social_pwa\WebPushManager->getSubscriptionsForUser(Object(Drupal\social_user\Entity\User))
#2 /app/html/modules/contrib/social_pwa/modules/activity_send_push/activity_send_push.module(24): Drupal\activity_send_push\Plugin\ActivitySend\PushActivitySend->process(Object(Drupal\activity_creator\Entity\Activity))
#3 [internal function]: activity_send_push_activity_insert(Object(Drupal\activity_creator\Entity\Activity))
#4 /app/html/core/lib/Drupal/Core/Extension/ModuleHandler.php(409): call_user_func_array(Object(Closure), Array)
#5 /app/html/core/lib/Drupal/Core/Extension/ModuleHandler.php(388): Drupal\Core\Extension\ModuleHandler->Drupal\Core\Extension\{closure}(Object(Closure), 'activity_send_p...')
#6 /app/html/core/lib/Drupal/Core/Extension/ModuleHandler.php(416): Drupal\Core\Extension\ModuleHandler->invokeAllWith('activity_insert', Object(Closure))

Proposed resolution

Add a check to make sure that user data is always as an array because get() has a mixed type of return value: array, null, bool.