Fix customProperties for optgroup options

[Zilus]

Description

This fixes bug with options inside optgroup not picking up the correct customProperties.

Types of changes

• Chore (tooling change or documentation change)
• Refactor (non-breaking change which maintains existing functionality)
• [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)

Checklist

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

[jonnitto]

I've tested this and it works as described. Would be happy for a merge and a release

[Xon]

#1166 implements a different solution