Check if `geo_location_data` is not NULL before using it

Hello,

I built your software with GeoIP enabled, and it crashed because my GeoIP database was not installed, and [`Geoip_new()`](https://github.com/allinurl/goaccess/blob/master/goaccess.c#L978) returned `NULL`.

I added a condition to skip the processing of the geolocation if the pointer to the geolocation data is `NULL`, and now it works with and without the GeoIP database.