(Inline Analytics) Fixes 3 issues:

  - undefined and NAN% was being displayed in text when student data didn't include correct or incorrect.
  - Items in radio display numbered incorrectly when student data missing options at the beginning.
  - Mouseover text included text from the correct and incorrect span.
Discussed F2F: this is is filter out `span`s with tick marks added to the container.

Please add a comment explaining this in code.