if(argc < 2 || !naIsGhost(args[0]) || \
naGhost_type(args[0]) != &PropNodeGhostType) \
naRuntimeError(c, "bad argument to props function"); \
if(argc < 2 || !naIsGhost(args[0]) || \
naGhost_type(args[0]) != &PropNodeGhostType) \
naRuntimeError(c, "bad argument to props function"); \