Error: RecordNotFound Couldn't find User with 'id'="

Fix: as outlined on [so](https://stackoverflow.com/a/44704987)

```ruby
def current_user
  @current_user ||= User.find_by(id: session[:user_id]) if session[:user_id]
end
```
---

Error: Tables not found in heroku error, such as in the case

`ActionView::Template::Error (PG::UndefinedTable: ERROR:  relation "events" does not exist`

Fix: as outlined on [so](https://stackoverflow.com/a/37372219)

In Heroku console: `rake run db:schema:load`