Handle (odd) corner case of argumentless __global__ function.

include/hip/hcc_detail/functional_grid_launch.hpp

@@ -102,6 +102,8 @@ inline std::vector<std::uint8_t> make_kernarg(
     static_assert(sizeof...(Formals) == sizeof...(Actuals),
         "The count of formal arguments must match the count of actuals.");
 
+    if (sizeof...(Formals) == 0) return {};
+
     const auto it = function_names().find(
         reinterpret_cast<std::uintptr_t>(kernel));