Fix What's New URL checking logic to compare port correctly

In a normal HTTP URL the port will be nil, which doesn't equal itself.

This bug was introduced by #1561 when it tried to add more granular
comparison to URL checking to allow for anchor links.

Author: ychin

src/MacVim/MMWhatsNewController.m

@@ -171,7 +171,7 @@ - (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigati
 
     if ([requestURL.scheme isEqual:_whatsNewURL.scheme] &&
         [requestURL.host isEqual:_whatsNewURL.host] &&
-        [requestURL.port isEqual:_whatsNewURL.port] &&
+        requestURL.port.integerValue == _whatsNewURL.port.integerValue &&
         [requestURL.path isEqual:_whatsNewURL.path] &&
         [requestURL.query isEqual:_whatsNewURL.query])
     {