Fix detecting empty device IDs

Description

Fixes a regression from #606, which caused us no longer skip empty device IDs.

fixes #619

Motivation and Context

While empty device ID are, actually, not good. They are accepted by Home Assistant (and abused in Blueprints quite a bit). Therefore, skipping makes sense to prevent bunch of bug report 🙄

How has this been tested?

Screenshots (if appropriate):

Types of changes

[x] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[ ] Other

Checklist

[x] My code follows the code style of this project.
[ ] My change requires a change to the documentation.
[ ] I have updated the documentation accordingly.

frenck / spook

Fix detecting empty device IDs #669