"Template file 'header.html' is not found" error while trying to save Design Configuration.

[hostep]

Preconditions

1. Magento 2.2-develop branch, current commit: f18377b
2. PHP 7.0.27

Steps to reproduce

1. Setup a clean Magento from the 2.2-develop using commit f18377b
2. Go into the backend to Content => Design => Configuration
3. Open either the Global or Website scoped configuration
4. Click 'Save and Continue'

Expected result

1. Configuration should be saved without errors

Actual result

1. We are getting the error: Something went wrong while saving this configuration: Template file 'header.html' is not found.

Discussion

Curiously enough, this only happens on the Global and Website scope, when trying the same on the Storeview scope, it works and we don't see this error.

[magento-engcom-team]

@hostep, thank you for your report.
We've acknowledged the issue and added to our backlog.

[AngelBS]

#MageTitansMX

[magento-engcom-team]

@AngelBS thank you for joining. Please accept team invitation here and self-assign the issue.