Asset (sprite, backdrop, ...) does not load after clicking - scratch-gui v5.1.33

[mvn2016]

Expected Behavior

After clicking on an asset (sprite, backdrop, sound, ...) from the list of assets it should load the asset to the stage or related editor.

Actual Behavior

After clicking an asset nothing loads.

Steps to Reproduce

Steps to reproduce the behavior:

1. clone and install https://github.com/scratchfoundation/scratch-gui.git (latest version is 5.1.33 now)
2. npm start
3. run scratch on localhost:8601 in a browser
4. click on 'Choose a Sprite'
5. select and click on a sprite
6. the sprite does not load

System Details

Any browser