In MR diff, clicking ellipsis too fast causes duplicated lines
## Description While reviewing gitlab-ce!23351, one of the files in the diff was not responding when I clicked the ellipsis to see more file content. I clicked it a handful of times and then got duplicated lines: ![Screen_Shot_2018-11-28_at_12.41.27_AM](/uploads/d514c62adbbf46adef697f9cc9ccc042/Screen_Shot_2018-11-28_at_12.41.27_AM.png)
issue