unnecessary try catch in middleware

[jonathanong]

i actually looked at the middleware now, and this entire catch block is unnecessary:

try {
    // bodyparser middlewares maybe store body in request.body
    // or you can just set csrf token header
    this.assertCSRF(this.request.body)
  } catch (err) {
    if (err.status === 403) {
      this.status = 403
      this.body = 'invalid csrf token'
    } else {
      this.throw(err)
    }
    return
  }

an upstream error handler should handle the rendering of the error