[YW][yugabyte#4661] Fix backups tab rendering issue

Summary: Fix backups tab rendering issue.

Test Plan: Run UI as usual, navigate to Backups tab several times for different universes

Reviewers: ram, andrew

Reviewed By: andrew

Subscribers: ui

Differential Revision: https://phabricator.dev.yugabyte.com/D8610

managed/ui/src/reducers/reducer_universe.js

@@ -190,7 +190,7 @@ export default function(state = INITIAL_STATE, action) {
     case FETCH_UNIVERSE_BACKUPS_RESPONSE:
       return setPromiseResponse(state, "universeBackupList", action);
     case RESET_UNIVERSE_BACKUPS:
-      return { ...state, error: null, "universeBackupList": setInitialState({})};
+      return setInitialState(state, 'universeBackupList', []);
 
     case CREATE_UNIVERSE_BACKUP:
       return setLoadingState(state, "createUniverseBackup", {});