BUG Reapply fix for cms crashing due to History.js blindly appending slashes to end of url

The same fix has been applied to LeftAndMain.js in another part of the file at https://github.com/tractorcow/sapphire/blob/79c727661144d556971c05cee81152d7a13bd59e/admin/javascript/LeftAndMain.js#L86