materio-d8/patches/hook_flag_access_id_on_null.patch

diff --git a/flag_lists.module b/flag_lists.module
index cd81104..3decec0 100644
--- a/flag_lists.module
+++ b/flag_lists.module
@@ -237,47 +237,49 @@ function flag_lists_flag_action_access($action, FlagInterface $flag, AccountInte
   // Allow both users flag and the corresponding template.
   // Currently only the users flag lists are accepted.
   // This needs to corrected to allow also global lists.
-  $flagListsService = Drupal::service('flaglists');
-  $flagLists = $flagListsService->getAllFlaggingCollections();
-  foreach ($flagLists as $flagList) {
-    if ($flag->id() == $flagList->getRelatedFlag()->id()) {
-      if ($flagList->getBaseFlag()->isGlobal()) {
-        // The flag list is global.
-        return AccessResult::allowedIfHasPermission($account,
-          'access global flag lists');
-      }
-      elseif ($flagList->getOwnerId() == $account->id()) {
-        // The flag list is owned by current user.
-        return AccessResult::allowedIfHasPermission($account,
-          'view own flag lists');
-      }
-      else {
-        // The user is allowed to see all flag lists.
-        return AccessResult::allowedIfHasPermission($account,
-          'view flag lists');
+  if ($flag){
+    $flagListsService = Drupal::service('flaglists');
+    $flagLists = $flagListsService->getAllFlaggingCollections();
+    foreach ($flagLists as $flagList) {
+      if ($flag->id() == $flagList->getRelatedFlag()->id()) {
+        if ($flagList->getBaseFlag()->isGlobal()) {
+          // The flag list is global.
+          return AccessResult::allowedIfHasPermission($account,
+            'access global flag lists');
+        }
+        elseif ($flagList->getOwnerId() == $account->id()) {
+          // The flag list is owned by current user.
+          return AccessResult::allowedIfHasPermission($account,
+            'view own flag lists');
+        }
+        else {
+          // The user is allowed to see all flag lists.
+          return AccessResult::allowedIfHasPermission($account,
+            'view flag lists');
+        }
       }
     }
-  }
-
-  // Check for access for the used template as well.
-  $flagTemplates = $flagListsService->getAllFlagForList();
-  foreach ($flagTemplates as $flagTemplate) {
-    if ($flag->id() == $flagTemplate->id()) {
-      // This is one of the template flags.
-      // But is it global?
-      $baseFlag = Drupal::service('flag')->getFlagById($flagTemplate->getBaseFlag());
-      if ($baseFlag->isGlobal()) {
-        return AccessResult::allowedIfHasPermission($account,
-          'access global flag lists');
-      }
-      else {
-        return AccessResult::allowedIfHasPermissions($account, [
-          'administer flag lists',
-          'view own flag lists',
-          'view flag lists',
-        ],
-          'OR'
-        );
+  
+    // Check for access for the used template as well.
+    $flagTemplates = $flagListsService->getAllFlagForList();
+    foreach ($flagTemplates as $flagTemplate) {
+      if ($flag->id() == $flagTemplate->id()) {
+        // This is one of the template flags.
+        // But is it global?
+        $baseFlag = Drupal::service('flag')->getFlagById($flagTemplate->getBaseFlag());
+        if ($baseFlag->isGlobal()) {
+          return AccessResult::allowedIfHasPermission($account,
+            'access global flag lists');
+        }
+        else {
+          return AccessResult::allowedIfHasPermissions($account, [
+            'administer flag lists',
+            'view own flag lists',
+            'view flag lists',
+          ],
+            'OR'
+          );
+        }
       }
     }
   }