Undefined property

Card.vue

computed: {
  ...mapState({
      isLoggedIn: 'auth/isLoggedIn',
      activities: 'auth/activities'
  }),

  booked() {
      return this.isLoggedIn ? this.activities.includes(this.activity.id) : false
  },
}

getters.js

const activities = (state) => {
    if (state.isLoggedIn && state.currentUser !== null) {
        state.activities = state.currentUser.activities.data.map((activity) => {
            return activity.id
        })
    }
}