Don't break authorization if the admin theme breaks our JS selector.

The oauth form has some niceties about disabling/enabling the action button at different times. Unfortunately, if the admin theme or a form alter happens to break our selector, it results in a JS error that causes the entire Oauth setup process to bail out, preventing the user from setting up Oauth. This seems like an unfortunate result for a form nicety, so this code helps protect us from such a case.