Fix uncaught query param encoding errors (#12741)

spec/middleware/handle_bad_encoding_middleware_spec.rb

@@ -0,0 +1,21 @@
+require 'rails_helper'
+
+RSpec.describe HandleBadEncodingMiddleware do
+  let(:app) { double() }
+  let(:middleware) { HandleBadEncodingMiddleware.new(app) }
+
+  it "request with query string is unchanged" do
+    expect(app).to receive(:call).with("PATH" => "/some/path", "QUERY_STRING" => "name=fred")
+    middleware.call("PATH" => "/some/path", "QUERY_STRING" => "name=fred")
+  end
+
+  it "request with no query string is unchanged" do
+    expect(app).to receive(:call).with("PATH" => "/some/path")
+    middleware.call("PATH" => "/some/path")
+  end
+
+  it "request with invalid encoding in query string drops query string" do
+    expect(app).to receive(:call).with("QUERY_STRING" => "", "PATH" => "/some/path")
+    middleware.call("QUERY_STRING" => "q=%2Fsearch%2Fall%Forder%3Ddescending%26page%3D5%26sort%3Dcreated_at", "PATH" => "/some/path")
+  end
+end