Spec update: add the empty host concept

Follows whatwg/url#260. This does not impact parsing, only validation and the URL record representation.

README.md

@@ -4,7 +4,7 @@ whatwg-url is a full implementation of the WHATWG [URL Standard](https://url.spe
 
 ## Current Status
 
-whatwg-url is currently up to date with the URL spec up to commit [4bf85a](https://github.com/whatwg/url/commit/4bf85a08da18ef367e093426abef776d59e8fb7b).
+whatwg-url is currently up to date with the URL spec up to commit [5807b2](https://github.com/whatwg/url/commit/5807b28261e44a47e31683230137da395ddc79d8).
 
 ## API
 

src/url-state-machine.js

@@ -1039,10 +1039,10 @@ URLStateMachine.prototype["parse path"] = function parsePath(c) {
       this.url.path.push("");
     } else if (!isSingleDot(this.buffer)) {
       if (this.url.scheme === "file" && this.url.path.length === 0 && isWindowsDriveLetterString(this.buffer)) {
-        if (this.url.host !== null) {
+        if (this.url.host !== "" && this.url.host !== null) {
           this.parseError = true;
+          this.url.host = "";
         }
-        this.url.host = null;
         this.buffer = this.buffer[0] + ":";
       }
       this.url.path.push(this.buffer);