fix nullsafe warnings

_define.php

@@ -10,7 +10,7 @@
  * @copyright Jean-Christian Denis
  * @copyright GPL-2.0 https://www.gnu.org/licenses/gpl-2.0.html
  */
-if (!defined('DC_RC_PATH')) {
+if (!defined('DC_RC_PATH') || is_null(dcCore::app()->auth)) {
     return null;
 }
 
@@ -22,7 +22,7 @@ $this->registerModule(
     [
         'requires'    => [['core', '2.25']],
         'permissions' => dcCore::app()->auth->makePermissions([
-            dcAuth::PERMISSION_CONTENT_ADMIN,
+            dcCore::app()->auth::PERMISSION_CONTENT_ADMIN,
         ]),
         'type'       => 'plugin',
         'support'    => 'http://forum.dotclear.org/viewtopic.php?pid=333002#p333002',

src/BackendBehaviors.php

@@ -114,6 +114,11 @@ class BackendBehaviors
 
     public static function adminAfterDashboardOptionsUpdate(?string $user_id): void
     {
+        // nullsafe
+        if (is_null(dcCore::app()->auth) || is_null(dcCore::app()->auth->user_prefs)) {
+            return;
+        }
+
         dcCore::app()->auth->user_prefs->get('dashboard')->put(
             'topWriterPostsItems',
             !empty($_POST['topWriterPostsItems']),
@@ -149,6 +154,11 @@ class BackendBehaviors
 
     private static function setDefaultPref(): array
     {
+        // nullsafe
+        if (is_null(dcCore::app()->auth) || is_null(dcCore::app()->auth->user_prefs)) {
+            return [];
+        }
+
         if (!dcCore::app()->auth->user_prefs->get('dashboard')->prefExists('topWriterPostsItems')) {
             dcCore::app()->auth->user_prefs->get('dashboard')->put(
                 'topWriterPostsItems',

src/Utils.php

@@ -24,6 +24,11 @@ class Utils
 {
     public static function posts(string $period, int $limit, bool $sort_desc = true): array
     {
+        // nullsafe
+        if (is_null(dcCore::app()->blog)) {
+            return [];
+        }
+
         $req = 'SELECT COUNT(*) AS count, U.user_id ' .
             'FROM ' . dcCore::app()->prefix . dcBlog::POST_TABLE_NAME . ' P ' .
             'INNER JOIN ' . dcCore::app()->prefix . dcAuth::USER_TABLE_NAME . ' U ON U.user_id = P.user_id ' .
@@ -82,6 +87,11 @@ class Utils
 
     public static function comments(string $period, int $limit, bool $sort_desc = true, bool $exclude = false): array
     {
+        // nullsafe
+        if (is_null(dcCore::app()->blog)) {
+            return [];
+        }
+
         $req = 'SELECT COUNT(*) AS count, comment_email ' .
         'FROM ' . dcCore::app()->prefix . dcBlog::POST_TABLE_NAME . ' P,  ' . dcCore::app()->prefix . dcBlog::COMMENT_TABLE_NAME . ' C ' .
         'WHERE P.post_id=C.post_id ' .