Do not special case null for URLUtils attributes

LayoutTests/fast/dom/HTMLAnchorElement/script-tests/set-href-attribute-host.js

 description('Test setting the host attribute of the URL in HTMLAnchorElement.');
 
 var a = document.createElement('a');
 
 debug("Basic test");
 a.href = "https://www.mydomain.com:8080/path/";
 a.host = "www.otherdomain.com:0";
 shouldBe("a.href", "'https://www.otherdomain.com:0/path/'");
 
 // IE8 throws "The URL is invalid" exception.
@@ skipping 27 matching lines @@
 a.href = "https://www.mydomain.com:8080/path/";
 a.host = "www.otherdomain.com: 443";
 shouldBe("a.href", "'https://www.otherdomain.com:0/path/'");
 
 // Firefox 3.5.2 removed the port, clearly against the spec .
 debug("Colon without port number");
 a.href = "https://www.mydomain.com:8080/path/";
 a.host = "www.otherdomain.com:";
 shouldBe("a.href", "'https://www.otherdomain.com:0/path/'");
 
-// IE8 converts null to "null", which is not the right thing to do.
-// Firefox 3.5.2 allows setting the host to null, which it shouldn't per
-// http://dev.w3.org/html5/spec/infrastructure.html#url-decomposition-idl-attributes .
 debug("Set host to null");
 a.href = "https://www.mydomain.com:8080/path/";
 a.host = null;
-shouldBe("a.href", "'https://www.mydomain.com:8080/path/'");
+shouldBe("a.href", "'https://null:8080/path/'");
 
 // Both IE8 and Firefox 3.5.2 allow setting the host to empty string, which they shouldn't, per
 // http://dev.w3.org/html5/spec/infrastructure.html#url-decomposition-idl-attributes .
 // Since both do that in a buggy way, WebKit does not follow either one of them.
 debug("Set host to empty string");
 a.href = "https://www.mydomain.com:8080/path/";
 a.host = "";
 shouldBe("a.href", "'https://www.mydomain.com:8080/path/'");
 
 // Firefox 3.5.2 does not `set the host for file: .
@@ skipping 40 matching lines @@
 } catch(e) {
 debug("Exception: " + e.description);
 }
 
 // Both IE8 and Firefox append the hosts, instead of rejecting, per
 // http://dev.w3.org/html5/spec/infrastructure.html#url-decomposition-idl-attributes .
 debug("Set host to a URL with tel: protocol");
 a.href = "tel:+1-816-555-1212";
 a.host = "+1-800-555-1212";
 shouldBe("a.href", "'tel:+1-816-555-1212'");