strange error (for me)

hello, i´m here again with a new question:
when i put
and model is not the panda or the enviroment that the program includes, whhen i run the game, this show my an error:
AtributeError:´NoneType´, objet has no atribute ´reparentTo´
i think it´s a silly question


im sorry for the question. i have the solution.