[✓][BUG] CE skips downloading missing tiles for levels with preview text

[Simon]

CE 1.1.1

This works:

• Have a level without preview text, but with missing tiles.
  
• Go to its preview screen. The level image contains some checkered question marks.
  
• Attempt to start the level.
  
• NL asks you: Missing tiles, do you want to download the tiles?
  
• Click: Yes.
  
• NL downloads the tiles.
  
• We're back in the preview screen, and the level previews normally.
  

This is a bug:

• Have a level with preview text, but with missing tiles.
  
• Go to its preview screen. The level image contains some checkered question marks.
  
• Attempt to start the level.
  
• NL proceeds to the separate screen that prints the preview text without the level preview image. We can read the custom text.
  
• Click again.
  
• We're playing the level and see lots of checkerboarded question marks instead of the terrain.
  

Expected instead: After step 3 of the failure, NL prompts us to download the missing tiles. You can download the tiles reasonably around step 3, 4, 5, but definitely before step 6 of the failure.

Throughout all this, I have activated the online features in the options.

Example level with preview text and downloadable tiles is Re-Enlistment by Giga. It's in the Level of the Year 2025 pack.

-- Simon

[WillLem]

The Preview Screen's CloseScreen procedure now only handles screen transitions. The check for missing pieces has been moved to BeginPlay, before transitioning to either gameplay or the preview text screen (if present).

This ensures that the check occurs no matter what the entry point, and we don't unnecessarily view the preview text screen if the level itself cannot be loaded due to missing pieces.

Fixed in NLCEPlayer commit b07faad.