Enable readability-container-size-empty tests

This one is a little trivial, but it does help in readability.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I5366d4eec8af2f781b3bad804131ae2eb806e3aa
diff --git a/redfish-core/lib/storage.hpp b/redfish-core/lib/storage.hpp
index f5e75e5..3e6f422 100644
--- a/redfish-core/lib/storage.hpp
+++ b/redfish-core/lib/storage.hpp
@@ -113,7 +113,7 @@
                 [asyncResp,
                  health](const boost::system::error_code ec,
                          const crow::openbmc_mapper::GetSubTreeType& subtree) {
-                    if (ec || !subtree.size())
+                    if (ec || subtree.empty())
                     {
                         // doesn't have to be there
                         return;