Alert page breaks when target query returns zero-length column name

[susodapop]

Issue Summary

This is similar to #4249.

Steps to Reproduce

1. Create a query with the query results data source: SELECT 1 ""
2. Make a new Alert and target the query from step one
3. Observe the Alert interface disappears.

I can only reproduce it with the query results data source because most other databases will not permit a zero-length column alias. If you run this query in Postgres the database raises an exception. But SQLite allows it so we see the error.

Technical details:

• Redash Version: v9 Alpha
• Browser/OS: FF, Safari, Chrome
• How did you install Redash: SaaS