Internal Server Error with certain LTI configurations (Redirect URIs)

[Dantemss]

Summary:

If any of the Redirect URIs in an LTI integration has a ? in it, and you try to launch a url with no querystring and no ?, Canvas blows up on this line: https://github.com/instructure/canvas-lms/blame/master/app/controllers/lti/ims/authentication_controller.rb#L233 because it tries to feed nil into CGI.parse()

Steps to reproduce:

1. Create LTI integration and make sure at least one of the Redirect URIs has a ?
2. Do an LTI launch with a redirect_uri with no ? and no querystring
3. Receive Internal Server Error from Canvas

Expected behavior:

Canvas should execute the launch successfully, assuming everything is configured properly.

Actual behavior:

Canvas displays an Internal Server Error screen.

Additional notes: