Avoid panic for "search flights on airline"

It prefers a fail job rather than a process panic

internal/handlers/acmesky/tm_search_flight_on_airline.go

@@ -33,7 +33,9 @@ func TMSearchFlightsOnAirline(client worker.JobClient, job entities.Job) {
 
  interests := variables["interests"].([]interface{})
  if index < 0 || index >= len(interests) {
- panic("Index out of range")
+ log.Errorf("Error for airline `%s`: index out of range %d", airline, index)
+ acmejob.FailJob(client, job)
+ return
  }
 
  flights := []map[string]interface{}{}