add defaul value for gather config

lib/tasks/cognigy/speech-config.js

@@ -24,7 +24,7 @@ class SpeechConfig extends Emitter {
     this.logger.debug({opts, sessionLevel: this.sessionConfig, turnLevel: this.turnConfig}, 'SpeechConfig updated');
   }
 
-  makeGatherTaskConfig({textPrompt, urlPrompt}) {
+  makeGatherTaskConfig({textPrompt, urlPrompt} = {}) {
     const opts = JSON.parse(JSON.stringify(this.sessionConfig || {}));
     const nextTurnKeys = Object.keys(this.turnConfig || {});
     const newKeys = nextTurnKeys.filter((k) => !(k in opts));