Allow for empty url

lib/UrlClassifier.js

@@ -83,11 +83,12 @@ UrlClassifier.prototype = {
     this._results = {};
     try {
       // submit url+title to workers
-      let uri = NetUtil.newURI(url);
+      let theUrl = url || "http://www.no_such_domain_ever.hmm";
+      let uri = NetUtil.newURI(theUrl);
       let host = getPlacesHostForURI(uri);
       let message = {};
       message.message = "getInterestsForDocument";
-      message.url = url;
+      message.url = theUrl;
       message.title = title || "";
       message.host = host;
       message.path = uri["path"];

test/test-UrlClassifier.js

@@ -42,7 +42,7 @@ exports["test url classifier"] = function test_UrlClassifier(assert, done) {
     });
 
     // classify only the text
-    results = yield urlClassifier.classifyPage("http://www.xyz.com", "iphone, ipad, apple, product, phone");
+    results = yield urlClassifier.classifyPage(null, "iphone, ipad, apple, product, phone");
     testUtils.isIdentical(assert, results["edrules"].results,
         [{"type":"rules","interests":[]},
          {"type":"keywords","interests":["Apple"]},