Small Javascript fixes

The first commit (3fa511336d5dc1596b33241e2064026f9c885749) fixes a small typo, making syntax highlighting for solution codes in the admin interface work. This also makes the file name in the title of the popup window appear.

The second commit (b7657032949df80a01dfa3541ac692283a883a68) replaces `href="#"` by `href="javascript:void(0);"` a few times in the admin interface. Otherwise, the page scrolls up every time you open the source code of a solution, for example. This can get quiet distracting if you have a lot of submissions and want to look through all of them.