Fix #5289: NoMethodError in /?search=.

app/controllers/application_controller.rb

@@ -248,7 +248,7 @@ class ApplicationController < ActionController::Base
   # => /tags?search[name]=touhou
   def normalize_search
     return unless request.get? || request.head?
-    params[:search] ||= ActionController::Parameters.new
+    params[:search] = ActionController::Parameters.new unless params[:search].is_a?(ActionController::Parameters)
 
     deep_reject_blank = lambda do |hash|
       hash.reject { |_k, v| v.blank? || (v.is_a?(Hash) && deep_reject_blank.call(v).blank?) }

test/functional/application_controller_test.rb

@@ -342,6 +342,20 @@ class ApplicationControllerTest < ActionDispatch::IntegrationTest
       assert_equal([tags[0].id], response.parsed_body.pluck("id"))
     end
 
+    should "remove blank `search` params from the URL" do
+      get tags_path(search: { name: "touhou", blah: "" }), as: :json
+
+      assert_redirected_to tags_path(search: { name: "touhou" })
+    end
+
+    should "ignore invalid `search` params" do
+      get tags_path(search: "foo"), as: :json
+      assert_response :success
+
+      get tags_path("search[]": "foo"), as: :json
+      assert_response :success
+    end
+
     should "support the expiry parameter" do
       get posts_path, as: :json, params: { expiry: "1" }