Scrub the invalid paramter value before using it in the error

You should be able to safely use the String error message. So when
finding the paramter has an invalid encoding we need to remove the
invalid bytes before using it in the error. Otherwise the caller might
get another Encoding error if they use the message.

actionpack/lib/action_dispatch/request/utils.rb

@@ -32,7 +32,7 @@ module ActionDispatch
           unless params.valid_encoding?
             # Raise Rack::Utils::InvalidParameterError for consistency with Rack.
             # ActionDispatch::Request#GET will re-raise as a BadRequest error.
-            raise Rack::Utils::InvalidParameterError, "Non UTF-8 value: #{params}"
+            raise Rack::Utils::InvalidParameterError, "Invalid encoding for parameter: #{params.scrub}"
           end
         end
       end

actionpack/test/dispatch/request_test.rb

@@ -1024,7 +1024,8 @@ class RequestParameters < BaseRequestTest
       request.path_parameters = { foo: "\xBE" }
     end
 
-    assert_equal "Invalid path parameters: Non UTF-8 value: \xBE", err.message
+    assert_predicate err.message, :valid_encoding?
+    assert_equal "Invalid path parameters: Invalid encoding for parameter: <20>", err.message
   end
 
   test "parameters not accessible after rack parse error of invalid UTF8 character" do