Can reproduce via http://petstore.swagger.io/#/?foo=bar
and the following error will be thrown:
Uncaught (in promise) DOMException: Failed to execute 'querySelector' on 'Document': '#operations-tag-?foo=bar' is not a valid selector.
The error doesn't seem to affect the demo page but it affects the usage of swagger-ui in our app from https://github.com/rynam0/ember-swagger-ui where the error is similar to the one listed, causing selectors to crash. Version of swagger-ui used is (2.2.10)