Error in custom dashboard yml file breaks the dashboards dropdown

Summary

If there is an error in the custom dashboard yml file the dashboards dropdown in the Monitoring dashboard breaks and makes it difficult to switch to another dashboard.

Steps to reproduce

1. Add a custom dashboard yml file instructions here https://docs.gitlab.com/ee/user/project/integrations/prometheus.html#adding-a-new-dashboard-to-your-project
2. Make sure that there is a mistake in yml file.
3. After the pipeline goes green navigate to the Monitoring dashboard within operations > metrics
4. Notice that there is a red warning message which is expected. However, the dashboards dropdown is empty and the user cannot select another dashboard.

What is the expected correct behavior?

The dashboards dropdown should continue to work so the user can try another dashboard.

Relevant logs and/or screenshots