fix post specs

app/models/post.rb

@@ -28,10 +28,10 @@ class Post < ApplicationRecord
   end
 
   def limit_of_post_per_day
-    posts_from_day = user.posts.where('created_at >= ?', Time.zone.now.beginning_of_day)
+    posts_from_day = user&.posts&.where('created_at >= ?', Time.zone.now.beginning_of_day)
 
-    if posts_from_day.count >= 5
-      errors.add(:base, 'You can post only 5 posts per day')
-    end
+    return if posts_from_day && posts_from_day.count < 5
+
+    errors.add(:base, 'You can post only 5 posts per day')
   end
 end