gather bugfix: dont start transcribing after call is gone

lib/tasks/gather.js

@@ -385,7 +385,7 @@ class TaskGather extends Task {
       }
     }
     if (evt.is_final) {
-      if (evt.alternatives[0].transcript === '') {
+      if (evt.alternatives[0].transcript === '' && !this.callSession.callGone) {
         this.logger.info({evt}, 'TaskGather:_onTranscription - got empty transcript, listen again');
         return this._startTranscribing(ep);
       }