Function meta_isnull

library/LuaWrapper.cpp:1121–1126

* Metamethod: df.isnull(obj) */

 * Metamethod: df.isnull(obj)
 */
static int meta_isnull(lua_State *state)
{
    luaL_checkany(state, 1);
    lua_pushboolean(state, Lua::IsDFNull(state, 1));
    return 1;
}

static int meta_nodata(lua_State *state)
{