Fixes 404 when request header Accept-Encoding not set

When static middleware is enabled, sending a request without
Accept-Encoding set would cause a premature call to pass()
before checking if the requested file exists. This meant that
calls to normal Express routes would be intercepted and result
in 404s.

lib/staticGzip.js

@@ -209,7 +209,6 @@ exports = module.exports = function staticGzip(dirPath, options){
             }
         }
 
-        if (!method) return pass(filename);
 
         fs.stat(filename, function(err, stat) {
 
@@ -221,6 +220,9 @@ exports = module.exports = function staticGzip(dirPath, options){
                 return next();
             }
 
+            // Check if file exists before passing uncompressed to client
+		        if (!method) return pass(filename);
+
             if (!contentTypeMatch.test(contentType)) {
                 return pass(filename);
             }