Vuex getter method returns undefined

I am trying to call a getter method and it's not getting called for some reason. If I console.log the store I can see that it's undefined:

This is where I'm calling the getter method:

computed: {
    client() {
        console.log(this.$store); //see above screenshot
        console.log(this.$route.params.id); //shows a valid value.
        //nothing seems to happen after this point, console.log in the below getter doesn't happen.
        return this.$store.getters['clients/clientById', this.$route.params.id];
    }
},

here's my getter in clients.js module:

 getters: {
    clients(state) {
        return state.clients;
    },
    hasClients(state) {
        return state.clients.length > 0;
    },
    clientById(state, id) {
        console.log('test'); //this doesn't happen
        return state.clients.find(client => client.id === id);
    }
}

The first 2 getter methods are working fine, using the same syntax as what I'm doing when I'm calling the clientById getter.

What I'm trying to accomplish is to have an array of client objects, and then when a user clicks on a client in the client list, I grab the ID out of the route params and the appropriate client data is displayed on the page. I'd appreciate any guidance on whether I'm approaching this in the right way as well as I'm new to Vue.

   state() {
     return {
       clients: [ 
         {
           id: null,
           client_name: '',
           address: '',
           city: '',
           state: '',
           zip:'',
           created_at: '',
           updated_at: '',
           deleted_at: null
         },
       ]
     };
   }, 

UPDATE:

I'll provide my entire clients.js module in case something is off with that. Everything else seems to be working fine, so not sure if this is related or not. This is an updated version of the getter where I changed it to an arrow function based on your feedback. When I do this, I get another error: TypeError: 'caller', 'callee', and 'arguments' properties may not be accessed on strict mode functions or the arguments objects for calls to them at Function.

I've also tried hard-coding the ID within the getter method and taking it out of the passed-in ID parameter, and that seems to work, but is returning undefined, so it's still not getting a value from state.

import axios from "axios";

export default {
    namespaced: true,
    state() {
        return {
            isLoading: false,
            clients: [ 
                    {
                        id: null,
                        client_name: '',
                        address: '',
                        city: '',
                        state: '',
                        zip:'',
                        created_at: '',
                        updated_at: '',
                        deleted_at: null
                    },
                ]
            };
      },
  mutations: {
    setLoadingStatus(state, status) {
        state.isLoading = status;
    },
    setClients(state, clients) {
        state.clients = clients;
    }
  },
  actions: {
    async fetchClients(context) {
        context.commit('setLoadingStatus', true);
        try {
            const resp = await axios.get('http://localhost/api/clients');
            context.commit('setLoadingStatus', false);
            context.commit('setClients', resp.data);
        } catch(e) {
            console.log(e);
        }
    }
  },
  getters: {
    clients(state) {
        return state.clients;
    },
    hasClients(state) {
        return state.clients.length > 0;
    },
    clientById: (state) => (id) => {
        return state.clients.find(client => client.id === id);
    }
  }
};