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

Conflicts:
	actionpack/CHANGELOG.md

1 files changed, 1 insertions, 1 deletions

diff --git a/actionpack/lib/action_dispatch/http/mime_negotiation.rb b/actionpack/lib/action_dispatch/http/mime_negotiation.rb
index b803ce8b6f..0b2b60d2e4 100644
--- a/actionpack/lib/action_dispatch/http/mime_negotiation.rb
+++ b/actionpack/lib/action_dispatch/http/mime_negotiation.rb
@@ -129,7 +129,7 @@ module ActionDispatch
           end
         end
 
-        order.include?(Mime::ALL) ? formats.first : nil
+        order.include?(Mime::ALL) ? format : nil
       end
 
       protected