title: "Source image could not be found" when using Symfony3 LiipImageBundle
body: <p>I have the following error message in my Symfony3 application:</p>
  
  <p><a href="https://i.stack.imgur.com/ArwEyl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ArwEyl.png" alt="error page"></a></p>
  
  <p>This is the Twig code, along with the imagine_filter:</p>
  
  <p><a href="https://i.stack.imgur.com/GYDwWl.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/GYDwWl.jpg" alt="Code in Twig + imagine_filter"></a></p>
  
  <p>This is the local URL generated after applying the LiipImage filter:</p>
  
  <blockquote>
    <p>localhost/symfony3/web/app_dev.php/media/cache/resolve/my_thumb/symfony3/web/images/uploads/5745ce2e628a9.png</p>
  </blockquote>
  
  <p>This is my config for liipimage and vichuploader:</p>
  
  <pre><code># VichUploader Configuration
  vich_uploader:
      db_driver: orm # or mongodb or propel or phpcr
      twig: true
      mappings:
          product_image:
              uri_prefix:         /images/uploads
              upload_destination: %kernel.root_dir%/../web/images/uploads/
              namer:              vich_uploader.namer_uniqid
              inject_on_load:     true
              delete_on_update:   true
              delete_on_remove:   true
  
  # liip_imagine Configuration
  liip_imagine:
      resolvers:
         default:
            web_path: ~
  
  
      filter_sets:
          cache: ~
          my_thumb:
              quality: 75
              filters:
                  thumbnail: { size: [120, 90], mode: outbound }
  </code></pre>
  
  <p>How can I fix it?</p>