title: Gridsome Graphql filter variable
body: <p>Im trying to query a collection and filter it depends on the $path var
  but it either returns empty or throwing an error</p>
  
  <pre><code>&lt;page-query&gt;
  query Gallery($path: String!){
    photos : allPhotos(filter: { nameFromGalleries: { contains: [$path]}}){
      edges{
        node{
          nameFromGalleries
          galleries
          attachments{
            thumbnails{
              full{
                url
              }
            }
          }
        }
      }
    }
  &lt;/page-query&gt;
  </code></pre>
  
  <p>for another query on the same page it works just fine </p>
  
  <pre><code>  gallery : gallery(path: $path){
      title
      children{
        name
        path
      }
    }
  </code></pre>