#70 standings.html reset inbetween contests

[Jaco Kroon]

When using /standings.html at ICPC I typically set up two contests pre-emptively, one for mock and one for real. When the switch happens the supportings standings.txt file changes from having content to being empty. This screws with the standings.html page and whilst it will flip to the new column names the existing teams remains in the list when really they should be cleared out.

A page reload fixes the problem so there exists an easy workaround but the user may not be aware of this. Potentially causing some confusion.