fix: update fallback SEO configuration to use null values for description and keywords

Author: cklei-carly

config/inspirecms.php

@@ -436,8 +436,8 @@
         'slug_generator' => DefaultSlugGenerator::class,
         'fallback_seo' => [
             'title' => env('APP_NAME', 'Home'),
-            'description' => 'Powered by InspireCMS',
-            'keywords' => '',
+            'description' => null,
+            'keywords' => null,
             'image' => null,
         ],
     ],

src/InspireCms.php

@@ -198,7 +198,7 @@ public function getFallbackLanguage(): ?LanguageDto
     }
 
     /**
-     * Get fallback SEO configuration
+     * Get fallback SEO
      *
      * @return SeoDto
      */