Bridges without geoip file report empty statistics

A bridge that doesn't have a geoip file reports empty statistics, implying that it saw zero users. That's confusing, because we cannot distinguish this case from a bridge that actually didn't see any users. The bridge should simply leave out its statistics if it doesn't have a geoip file.

There are not many bridges affected by this bug, but we should probably fix it anyway. 0.2.3.x or 0.2.4.x?