Return null type format when format is not know

When requesting a controller with the following code with a unknown format:

    def my_action
      respond_to do |format|
        format.json { head :ok }
        format.any { render text: 'Default response' }
      end
    end

we should render the default response instead of raising ActionController::UnknownFormat

Fixes #14462

Conflicts:
	actionpack/CHANGELOG.md
	actionpack/test/controller/mime/respond_with_test.rb

actionpack/CHANGELOG.md

@@ -1,3 +1,10 @@
+*   Returns null type format when format is not know and controller is using `any`
+    format block.
+
+    Fixes #14462.
+
+    *Rafael Mendonça França*
+
 *   Only make deeply nested routes shallow when parent is shallow.
 
     Fixes #14684.

actionpack/lib/action_dispatch/http/mime_negotiation.rb

@@ -129,7 +129,7 @@ def negotiate_mime(order)
           end
         end
 
-        order.include?(Mime::ALL) ? formats.first : nil
+        order.include?(Mime::ALL) ? format : nil
       end
 
       protected

actionpack/test/controller/mime/respond_to_test.rb

@@ -492,6 +492,11 @@ def test_handle_any_any_xml
     assert_equal 'Whatever you ask for, I got it', @response.body
   end
 
+  def test_handle_any_any_unkown_format
+    get :handle_any_any, { format: 'php' }
+    assert_equal 'Whatever you ask for, I got it', @response.body
+  end
+
   def test_browser_check_with_any_any
     @request.accept = "application/json, application/xml"
     get :json_xml_or_html