Screenshots are blank in the Deferred Technical Preview

Steps to reproduce:

1. Import any resource pack with PBR capabilities
2. Enable the experimental toggle for Render Dragon features
3. Switch rendering mode to "Deferred Technical Preview"
4. Take a screenshot using the button in the pause menu
5. Go to Profile -> Screenshot gallery and look at the screenshot

Observed result:
Only the sky is visible in the screenshot.

Expected result:
The world is visible in the screenshot.