Fix for themed background in datagrid

[Mil4n0r]

Checklist
(Check off all the items before submitting)

• Build process is done without errors. All tests pass in the /lib directory.
• Self-reviewed the code before submitting.
• Meets accessibility standards.
• Added/updated documentation to /website as needed.
• Added/updated tests as needed.

Purpose
Fix background color inside Datagrid being set based on the local theme, which is visible under certain conditions such as a fixed height container wrapping it.