handle case where the course_instance is mapped to an iSite and an external site
Don’t show topic locator link if topic id is not set
Merge branch 'feature/Reserves' into develop

# By Colin Murtaugh (1) and Mysore, Sapna (1)
* feature/Reserves:
  Don’t show topic locator link if topic id is not set
  handle case where the course_instance is mapped to an iSite and an external site