feat: バグ直し（#223） (#224)

#223

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #224

backend/app/controllers/posts_controller.rb

@@ -44,7 +44,11 @@ class PostsController < ApplicationController
               nil
             end
       end
-    }, count: filtered_posts.count(:id), next_cursor: }
+    }, count: if filtered_posts.group_values.present?
+      filtered_posts.count.size
+    else
+      filtered_posts.count
+    end, next_cursor: }
   end
 
   def random
@@ -181,7 +185,7 @@ class PostsController < ApplicationController
   private
 
   def filtered_posts
-    tag_names = params[:tags]&.split(' ')
+    tag_names = params[:tags].to_s.split(' ')
     match_type = params[:match]
     if tag_names.present?
       filter_posts_by_tags(tag_names, match_type)