Fixed users table migration allowing email/password registration

[ghost]

 [Illuminate\Database\QueryException]
  SQLSTATE[23000]: Integrity constraint violation: 19 NOT NULL constraint failed: users.oauth_provider (SQL: insert into "users" ("id", "name", "email", "password", "email_verified", "created_at") valu
  es (1, admin, admin@example.com, y$WP.pIKU4WTSw2bAocXwrqer.ii6kTQHJw/QABQtgxWoDNKJwVtuAu, 1, 2016-06-06 20:53:55))

  [PDOException]
  SQLSTATE[23000]: Integrity constraint violation: 19 NOT NULL constraint failed: users.oauth_provider

The following columns must be null in order to seed the database properly:

• oauth_provider
• oauth_provider_id
• avatar
• email_verification_code

Same error turns up when registering from the frontend too.

[silverbux]

awesome thanks!