server.DeleteMessage catches channel or client==nil

Fixes #2020

Calling /msg histserv delete #wrongchan <msgid> returns spurrious success
message. Calling /msg histserv delete <randomchars> <msgid> returns
similar message.

These would lead to the pointer hist == nil, and
server.historyDB.DeleteMsgid() would return nil.

Returns errNoSuchChannel or errInvalidTarget if channel or client == nil

irc/errors.go

@@ -54,6 +54,7 @@ var (
  errConfusableIdentifier = errors.New("This identifier is confusable with one already in use")
  errInsufficientPrivs = errors.New("Insufficient privileges")
  errInvalidUsername = errors.New("Invalid username")
+ errInvalidTarget = errors.New("Invalid target")
  errFeatureDisabled = errors.New(`That feature is disabled`)
  errBanned = errors.New("IP or nickmask banned")
  errInvalidParams = utils.ErrInvalidParams

irc/server.go

@@ -1061,13 +1061,17 @@ func (server *Server) DeleteMessage(target, msgid, accountName string) (err erro
  if status, _, _ := channel.historyStatus(config); status == HistoryEphemeral {
  hist = &channel.history
  }
+ } else {
+ return errNoSuchChannel
  }
  } else {
  client := server.clients.Get(target)
  if client != nil {
  if status, _ := client.historyStatus(config); status == HistoryEphemeral {
  hist = &client.history
  }
+ } else {
+ return errInvalidTarget
  }
  }
  }