Ember continue create model even when request error

I have ember model like this:

import DS from 'ember-data';

export default DS.Model.extend({        
    sportType: DS.attr('string'),       
    fallbackLogo: function(){
        return 'assets/images/markers-png/marker-'+this.get('sportType').toLowerCase()+'-gray.png';
    }.property('sportType')
})

but even the request for find() got response error

GET http://ift.tt/1KJEQK9 404 (Not Found)

the model still try to create itself thus trigger error

Uncaught TypeError: Cannot read property 'toLowerCase' of undefined

how i can handle request error?