Do not special case null for URLUtils attributes

LayoutTests/fast/dom/HTMLAnchorElement/set-href-attribute-host-expected.txt

 Test setting the host attribute of the URL in HTMLAnchorElement.
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
 
 Basic test
 PASS a.href is 'https://www.otherdomain.com:0/path/'
 Set host with '?' in it
 FAIL a.href should be https://www.other/?domain.com:8080/path/?key=value. Was https://www.other%3Fdomain.com:8080/path/?key=value.
 Set default port for another protocol
 PASS a.href is 'https://www.otherdomain.com:80/path/'
 Set default port
 PASS a.href is 'https://www.otherdomain.com/path/'
 Set host with letters in port number
 PASS a.href is 'https://www.otherdomain.com:44/path/'
 Leading space in port number
 PASS a.href is 'https://www.otherdomain.com:0/path/'
 Colon without port number
 PASS a.href is 'https://www.otherdomain.com:0/path/'
 Set host to null
-PASS a.href is 'https://www.mydomain.com:8080/path/'
+FAIL a.href should be https://null:8080/path/. Was https://null/path/.

[arv (Not doing code reviews), 2013/10/07 21:23:42]

This is https://code.google.com/p/chromium/issues/detail?id=304946

 Set host to empty string
 PASS a.href is 'https://www.mydomain.com:8080/path/'
 Set host to URL with file: protocol
 PASS a.href is 'file://mydomain.com/path/'
 Set host containing slashes in it
 FAIL a.href should be https://www.otherdom/ain.com/path/. Was https://www.otherdom%2Fain.com/path/.
 Set host to a malformed URL
 FAIL a.href should be https:/
 ww.my@domain.com:8080/path/. Was https://ww.my@www.other%21domain.com:15/path/.
 Set host that starts with ':'
 PASS a.href is 'https://domain.com:8080/path/'
 Set host to URL containing username and ..
 FAIL a.href should be https://rwwmy@www.other!domain.com:25/pa..th/. Was https://rwwmy@www.other%21domain.com:25/pa..th/.
 Set host to a URL with tel: protocol
 PASS a.href is 'tel:+1-816-555-1212'
 PASS successfullyParsed is true
 
 TEST COMPLETE