more consistent behavior of CurrentUser.root_url

app/controllers/application_controller.rb

@@ -176,7 +176,7 @@ class ApplicationController < ActionController::Base
   def reset_current_user
     CurrentUser.user = nil
     CurrentUser.ip_addr = nil
-    CurrentUser.root_url = root_url
+    CurrentUser.root_url = root_url.chomp("/")
   end
 
   def set_started_at_session

app/logical/current_user.rb

@@ -59,7 +59,7 @@ class CurrentUser
   end
 
   def self.root_url
-    Thread.current[:current_root_url] || "https://#{Danbooru.config.hostname}/"
+    Thread.current[:current_root_url] || "https://#{Danbooru.config.hostname}"
   end
 
   def self.root_url=(root_url)

app/logical/storage_manager.rb

@@ -14,7 +14,7 @@ class StorageManager
   end
 
   def default_base_url
-    CurrentUser.root_url + "data"
+    "#{CurrentUser.root_url}/data"
   end
 
   # Store the given file at the given path. If a file already exists at that