Function index_fail

extlibs/sol3/include/sol/sol.hpp:21118–21128

	};

	inline int index_fail(lua_State* L) {
		if (lua_getmetatable(L, 1) == 1) {
			int metatarget = lua_gettop(L);
			stack::get_field<false, true>(L, stack_reference(L, raw_index(2)), metatarget);
			return 1;
		}
		// With runtime extensibility, we can't
		// hard-error things. They have to
		// return nil, like regular table types
		return stack::push(L, lua_nil);
	}

	inline int index_target_fail(lua_State* L, void*) {
		return index_fail(L);