Prevent incorrect tuple size on get_extra_info errors

According to https://docs.python.org/3/library/asyncio-protocol.html#asyncio.BaseTransport.get_extra_info,
get_extra_info fails by returning None. This is an attempt in
normalization of the response in cases of AF_INET, AF_INET6 and
erroneous return values.

sanic/request.py

@@ -143,7 +143,7 @@ class Request(dict):
     @property
     def ip(self):
         if not hasattr(self, '_ip'):
-            self._ip = self.transport.get_extra_info('peername')
+            self._ip = self.transport.get_extra_info('peername') or (None, None)
         return self._ip
 
     @property