Let geohash handle null island

and add test

parsers/geohash/70-geohash.js

@@ -69,6 +69,7 @@ module.exports = function(RED) {
                         var len = parseInt(value.precision || 9);
                         if (len < 1) { len = 1; }
                         if (len > 9) { len = 9; }
+                        value.precision = len;
                         if (typeof lat === 'number' && typeof lon === 'number') {
                             value.geohash = geohash.encode(lat, lon, len);
                             RED.util.setMessageProperty(msg,node.property,value);

parsers/geohash/package.json

@@ -1,9 +1,9 @@
 {
     "name"          : "node-red-node-geohash",
-    "version"       : "0.1.9",
+    "version"       : "0.1.10",
     "description"   : "A Node-RED node to encode and decode lat,lon pairs to a geohash.",
     "dependencies"  : {
-        "ngeohash"   : "0.6.0"
+        "ngeohash"   : "^0.6.3"
     },
     "repository" : {
         "type":"git",