World icons are not dumped to the screenshots/debug folder

The bug

When using F3+S to export all dynamic textures, the icons for resource packs will be copied to this folder. The icons for worlds, however, will not be.

How to reproduce

1. Use F3+S
2. Inspect the folder contents

Expected results

Both the world icons and resource pack icons would be present.

Actual results

Resource pack icons are present, but world icons are not.