404 error when clicking on commits in branch review if FishEye is not licensed

During the creation of a branch review, having only a Crucible license in place, if the user clicks in the commit link presented while adding content to the review Crucible opens a page with a 404 Page Not Found error, since the page it's linking to is a FishEye page showing the diff for the commit.

Steps to Reproduce

1. Have Crucible without a FishEye license.
2. Create a new review, selecting Choose Branches in the Add content screen.
3. Select the branch for which you want to create the review, then try clicking in a commit hash:
   
4. Crucible shows a 404 Page Not Found error:
   
   The following shows up in the logs:

   2015-07-13 16:41:50,504 DEBUG [qtp1441798206-172 ] fisheye ProfilingServletFilter-logRequest - start request GET /changelog/git?cs=fe4abe880307d2cf50239ed7246d8fea70b1ba58 sessionid=19ym7wt707clbzxxf8vw40fsw
   2015-07-13 16:41:50,508 INFO  [qtp1441798206-172 ] fisheye ServletUtils-send404 - 404: Page not found referer=http://localhost:8060/plugins/servlet/branchreview?reviewId=CR-19
   2015-07-13 16:41:50,572 DEBUG [qtp1441798206-172 ] fisheye ProfilingServletFilter-logRequest - end request in 68ms GET /changelog/git?cs=fe4abe880307d2cf50239ed7246d8fea70b1ba58 sessionid=19ym7wt707clbzxxf8vw40fsw 404