Don't symbolize params.

app/controllers/uploads_controller.rb

@@ -52,13 +52,13 @@ class UploadsController < ApplicationController
 
   def upload_model
     upload_models = {
-      user: User,
-      project: Project,
-      note: Note,
-      group: Group
+      "user"    => User,
+      "project" => Project,
+      "note"    => Note,
+      "group"   => Group
     }
 
-    upload_models[params[:model].to_sym]
+    upload_models[params[:model]]
   end
 
   def upload_mount