Fix clang-tidy issue

When running CI build, clang-tidy gives "missing 'typename' prior to
dependent type name" error, casuing build failure.

Fixes c8447d5 ("added support for optionals in unpackProperties")

Change-Id: I5d79a520815173e70ee3b6c4da306ae17f9a41d8
Signed-off-by: Jiaqing Zhao <jiaqing.zhao@intel.com>
diff --git a/include/sdbusplus/asio/property.hpp b/include/sdbusplus/asio/property.hpp
index 7dbec52..509bb77 100644
--- a/include/sdbusplus/asio/property.hpp
+++ b/include/sdbusplus/asio/property.hpp
@@ -30,8 +30,8 @@
 {
     using arg1_type =
         std::tuple_element_t<1, boost::callable_traits::args_t<Handler>>;
-    using arg1_pair_type = std::decay_t<arg1_type>::value_type;
-    using arg1_value_type = arg1_pair_type::second_type;
+    using arg1_pair_type = typename std::decay_t<arg1_type>::value_type;
+    using arg1_value_type = typename arg1_pair_type::second_type;
     getAllProperties<arg1_value_type>(bus, service, path, interface,
                                       std::forward<Handler>(handler));
 }