Unneeeded check as githubWebUri is guaranteed non-null at this point.

Personally, I'm fine with having a defensive check like this, but @skottler didn't seem to like this in a review comment in https://github.com/jenkinsci/github-oauth-plugin/pull/15/files so I'm respecting his opinion by removing this check.

src/main/java/org/jenkinsci/plugins/GithubSecurityRealm.java

@@ -394,10 +394,6 @@ public HttpResponse doFinishLogin(StaplerRequest request)
      * Returns the proxy to be used when connecting to the given URI.
      */
     private HttpHost getProxy(String uri) {
-        if (uri == null) {
-            return null;
-        }
-
         String prefix = uri.startsWith("https") ? "https" : "http";
         String proxyHost = System.getProperty(prefix + ".proxyHost");
         if (StringUtils.isBlank(proxyHost)) {