Bugfix: allow None type for dashboard title

[d-swift]

Change description

Closes #626 content validation bug where a dashboard have title=None. I suspect this is from lookml dashboards.

Type of change

• Bug fix (fixes an issue)
• New feature (adds functionality)

Related issues

Closes #626

Checklists

I was unable to run full test suite locally. I can run if you can share API credentials for your test Looker instance.

Security

• Security impact of change has been considered
• Code follows security best practices and guidelines

Code review

• Pull request has a descriptive title and context useful to a reviewer

[DylanBaker]

Thanks @d-swift!

I think there's one additional place this needs to be addressed, but I'm not sure what the right way to do it it. The title is used in the print out of the results, so we'll need to defer to something else. Relevant code is here.

Is it at all clear why this content doesn't have a title in your instance? We could defer to something like tile_title, but I'd want to make sure that's present.

[joshtemple]

@DylanBaker, we relaxed the content type to allow all other possible content types. It's possible some of these just don't have titles (we would have been skipping them and warning previously).

[DylanBaker]

@joshtemple I think in that case it's possible the printing in the CLI and the reporting in the app might not be working for other content types. Is that possible?

[DylanBaker]

Closing this. Going to be covered in #651