title: React native mapbox issue
body: <p>i'm trying to use mapbox in reactnative and as documented i follow everything
  but my app broking.
  please find the below exception for your reference
  <strong>null is not an object (evaluating 'MapboxGL.StyleURL').</strong>
  Please help me</p>
  <p><img src="https://i.stack.imgur.com/P8y5t.jpg" alt="" /></p>