Renderer rendererFound;
//If TryGetComponent doesn't find a Renderer on this, it returns false
//If a Renderer is found, it return true AND places the renderer that was 
//found into 'rendererFound'
if (TryGetComponent(out rendererFound) == false) 
{
  Debug.LogError($"Error in {GetType()}: GameObject doesn't have a Renderer object");
  return null;
}
//Use 'rendererFound' asif component was found
float halfRadius = rendererFound.bounds.size.z / 2;