avoid crashing on undetermined locations

this works around what is probably a bug in pygeoip:

    01:21:44 <@anarcat> .ip 10.0.0.1
    01:21:49 <peoplesmic> AttributeError: 'NoneType' object has no attribute 'get' (file "/usr/local/lib/python3.4/dist-packages/pygeoip/__init__.py", line 491, in country_name_by_addr)

it seems that, even internally, pygeoip doesn't handle very well
addresses that have no location defined... this patch should fix the
problem in willie until it is fixed upstream.