/r: handle trailing garbage chars

fixes https://console.cloud.google.com/errors/CO-fpZfMq_6ktgE

redirect.py

@@ -48,7 +48,7 @@ def redir(to):
     domains = set((util.domain_from_link(to),
                    urllib.parse.urlparse(to).hostname))
     for domain in domains:
-        if MagicKey.get_by_id(domain):
+        if domain and MagicKey.get_by_id(domain):
             logging.info(f'Found MagicKey for domain {domain}')
             break
     else:

tests/test_redirect.py

@@ -39,6 +39,10 @@ class RedirectTest(testutil.TestCase):
         self.assertEqual(301, got.status_code)
         self.assertEqual('https://foo.com/bar', got.headers['Location'])
 
+    def test_redirect_trailing_garbage_chars(self):
+        got = self.client.get(r'/r/https://v2.jacky.wtf\"')
+        self.assertEqual(404, got.status_code)
+
     def test_as2(self):
         self._test_as2(common.CONTENT_TYPE_AS2)