code: func PanicFilter(c *Controller, fc []Filter) {
  	defer func() {
  		if err := recover(); err != nil {
  			handleInvocationPanic(c, err)
  		}
  	}()
  	fc[0](c, fc[1:])
  }
docs: // PanicFilter wraps the action invocation in a protective defer blanket that
  // converts panics into 500 error pages.