Launcher shows a warning when first trying to download a new version of the asset index

The bug

When the launcher notices that there's a new version of the asset index available, it first shows the following warning instead of just downloading the new assets.

This issue usually happens when a snapshot has been released but not downloaded yet. The first try of clicking onto the "Play" button will fail in this case, but after that the game will be able to launch successfully.

Failed to download file, the file contents differ from what was expected.
Name: 1.15.json
URL: https://launchermeta.mojang.com/v1/packages/a3168de4f437fda8464afbaeb28866ee5b279426/1.15.json
Filename on disk: 1.15.json
Path: D:\Users\Daniel\Games\Minecraft\AppData\assets\indexes\1.15.json
Exists: File