fix: remove errors for joins option

[akaJes]

When used model.graphql.joins = true option appears some errors:

  "errors": [
    {
      "message": "Cannot read property 'associations' of undefined",

AND

  "errors": [
    {
      "message": "FIELD is associated to TABLE using an alias. You must use the 'as' keyword to specify the alias within your include statement.",

[alirizwan]

Thank you for the PR. I will test tonight and merge - release