Log message for non-SteamClient interface

Added debug print statement for interface check.

dll/dll.cpp

@@ -329,6 +329,7 @@ static void *create_client_interface(const char *ver)
         client_ptr->report_missing_impl(ver, EMU_FUNC_NAME);
     }
     
+    PRINT_DEBUG("%s interface is not SteamClient, returning nullptr!", ver);
     // Original steam returns 0 here.
     return nullptr;
 }