Dashboard can be created without sheet name

[dengmingtong]

Summary

I can create a dashboard without sheet name.

1. Create dashboard (input dashboard name and description, but not input sheet name)
2. Dashboard can be created successfully
3. We still can choose this dashboard when we try to save the visualization to dashboard. But there is no sheet display in Sheet drop down.

Steps to reproduce

What is the current bug behavior?

What is the expected correct behavior?

Relevant logs and/or screenshots

Possible fixes

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This is 🐛 Bug Report