The test is trying to access a non-existent property.
collections[5439] only has a property for 'album', so you need to test first to see if the property you want is there, and if it’s not, create one.
Also, I don’t believe you can use push to alter any of the properties besides tracks, because it is an array. The rest are string primitives.
Hope this helps! I had a really tough time with this one too.