Lack of prompt information

Created by: wenxin-01

Preset conditions 1、There is account A, which has cluster management privileges. 2、Use account A to log in to KS, and go to Platform management--》Cluster "B" management--》Alerting Policies.

To Reproduce Steps to reproduce the behavior:

1. Click 'create'
2. Click 'next' after enter name
3. Enter alarm rule
4. Click 'next'

Expected behavior Prompt that no monitoring target is selected Actual behavior There is no prompt on the page

/priority medium /area alerting /cc @leoendless /kind bug /milestone 3.1.0