initialize search params to avoid repeated nil checks

app/controllers/application_controller.rb

@@ -5,6 +5,7 @@ class ApplicationController < ActionController::Base
   before_filter :set_current_user
   after_filter :reset_current_user
   before_filter :set_title
+  before_filter :normalize_search
   before_filter :set_started_at_session
   before_filter :api_check
   layout "default"
@@ -100,4 +101,8 @@ protected
   def set_title
     @page_title = Danbooru.config.app_name + "/#{params[:controller]}"
   end
+
+  def normalize_search
+    params[:search] ||= {}
+  end
 end