P4 - Only player-characters can play

Most problems are detected when Inform translates the source text, but this is one of the exceptions, a "run-time problem" which emerges only during play.

Although Inform allows us to change the identity of the protagonist - the person through which the simulated world is seen and acted upon - only things of the kind player-character can be protagonists. Here, you seem to have tried to change the player to something which is not a player-character.