Fixed GeoIP lookup causing an exception when no MMDB is available.

src/Net/GeoIP.php

@@ -17,6 +17,11 @@ final class GeoIP {
         return self::$geoip;
     }
 
+    public static function isAvailable(): bool {
+        return !empty(self::$geoipDbPath)
+            && is_file(self::$geoipDbPath);
+    }
+
     public static function resolveCountry(string $ipAddress) {
         return self::getReader()->country($ipAddress);
     }

src/Net/IPAddress.php

@@ -23,6 +23,9 @@ final class IPAddress {
     }
 
     public static function country(string $address, string $fallback = 'XX'): string {
+        if(!GeoIP::isAvailable())
+            return $fallback;
+
         try {
             return GeoIP::resolveCountry($address)->country->isoCode ?? $fallback;
         } catch(AddressNotFoundException $e) {