When the diff file index is in docked mode, and the user switches which page was visible, we would hit an error and the file index would fail to update as the diff was loading, leaving every file showing a spinner. The problem is that when the page is scrolled, we redock the items table elsewhere onto the page. Inside the `#update()` method we would load all the new items, but then reset the `#$items` variable to be `tr` (grand)children of the view's element, which was empty because the table was a child of the banner instead. I've updated it to explicitly set `#$items` to be `tr` children of the items table. While in here, I realized that the way we're assembling the items table is quite inefficient, so I fixed this up to assemble all the child nodes first and then add them all to the DOM at the same time. Testing Done: - Ran js-tests. - Switched around between pages of a very large diff. Made sure that the paginators at both the top and bottom of the page worked correctly.