fixes #2501: Popular searches broken

app/logical/popular_search_service.rb

@@ -16,7 +16,7 @@ class PopularSearchService
 
     Cache.get("ps-#{scale}-#{dates}", 1.minute) do
       url = URI.parse("#{Danbooru.config.report_server}/hits/#{scale}?date=#{dates}")
-      response = []
+      response = ""
       Net::HTTP.start(url.host, url.port, :use_ssl => url.is_a?(URI::HTTPS)) do |http|
         http.read_timeout = 1
         http.request_get(url.request_uri) do |res|
@@ -28,4 +28,4 @@ class PopularSearchService
       response
     end
   end
-end
+end