fix phases

Author: ThomasKranitsas

src/services/ChallengeService.js

@@ -1414,7 +1414,7 @@ async function update (currentUser, challengeId, data, isFull) {
     if (finalStatus !== constants.challengeStatuses.New && finalTimelineTemplateId !== challenge.timelineTemplateId) {
       throw new errors.BadRequestError(`Cannot change the timelineTemplateId for challenges with status: ${finalStatus}`)
     }
-  } else {
+  } else if (finalTimelineTemplateId !== challenge.timelineTemplateId) {
     // make sure there are no previous phases if the timeline template has changed
     challenge.phases = []
   }