SBBSCTRL:User->Truncate Deleted Users menu item doesn't truncate index

The user index (data/user/name.dat) isn't truncated to match the proper length which can trigger an error message from the terminal server (e.g. upon startup or recycle):

User index (..\data\user/name.dat) length (189) does not match expected length (162), corruption suspected

The index will be fixed during the next daily maintenance event (midnight).

Found/reported by plt in IRC.