The upper part of the UI with the file panes and the lower part with the metadata box and cover art are separated by a splitter. The user can change the size distribution between both parts by dragging the splitter in between. This is good.

Both the upper and lower parts have minimum size hints, but but by completely dragging the splitter up or down the user can completely hide any of those parts. This results in a UI that appears broken, and without any hint to the user that there is a missing part and that they can make it visible again.

Prevent the complete hiding of these UI elements and show them at least with their minimum size. Should there be a real use case in hiding either the upper or lower part completely we could do so with an explicit action in the view menu.