guard against req.url being falsy

it's tempting to simply stop looking at req.url.path altogether, since that was introduced for hapi 17 in pinojs@83d58a7#diff-2c4782cb20f7f0d7ca90c7bc04939f4420c4bdb42fdce618984da393ba9202f7R60 .

but since pinojs#29 we look at req.path first, which is safer in hapi, so hapi doesn't care about req.url.path anymore.

but perhaps someone else does depend on req.url.path . so for now, continuing to look at req.url.path , which means a bit more guarding in the req serializer.

lib/req.js

@@ -76,7 +76,7 @@ function reqSerializer (req) {
   } else {
     const path = req.path
     // path for safe hapi compat.
-    _req.url = typeof path === 'string' ? path : (req.url.path || req.url)
+    _req.url = typeof path === 'string' ? path : (req.url ? req.url.path || req.url : undefined)
   }
   _req.headers = req.headers
   _req.remoteAddress = connection && connection.remoteAddress

test/req.test.js

@@ -274,6 +274,25 @@ test('req.url will be obtained from input request url when req path is a functio
   }
 })
 
+test('req.url being undefined does not throw an error', function (t) {
+  t.plan(1)
+
+  const server = http.createServer(handler)
+  server.unref()
+  server.listen(0, () => {
+    http.get(server.address(), () => {})
+  })
+
+  t.teardown(() => server.close())
+
+  function handler (req, res) {
+    req.url = undefined
+    const serialized = serializers.reqSerializer(req)
+    t.equal(serialized.url, undefined)
+    res.end()
+  }
+})
+
 test('can wrap request serializers', function (t) {
   t.plan(3)