title: Cannot read property toLowerCase of undefined using Adonis and PostgreSQL
body: <p>I'm using Adonis with PostgreSQL and I am trying to implement a search where a user would be able to search through posts using the <code>title</code></p>
  
  <p>I have my code structured like so</p>
  
  <pre><code>&lt;form action="{{ route('search') }}" method="GET" style="outline:none"&gt;
    &lt;input class="shadow appearance-none border-2 p-2 h-10" style="outline:none" type="text" name="q" placeholder="Search the forum" value="{{ request.input('q', '') }}"&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>and my controller like so</p>
  
  <pre><code>'use strict'
  
  const Post = use('App/Models/Post')
  const Database = use('Database')
  
  class SearchController {
    async index ({ view, request, response, params }) {
      let posts = await Post.query()
        .forIndex()
        .whereRaw('lower(title) LIKE ?', params.searchString.toLowerCase())
        .paginate(request.input('page', 1), 10)
  
      return view.render('index', {
        posts
      })
    }
  }
  
  module.exports = SearchController
  </code></pre>
  
  <p>However, I am getting the following error:</p>
  
  <p><img src="https://i.gyazo.com/thumb/1200/4d7b90d1cf957fd649a9a6426a03a4da-png.jpg" alt="error"></p>