When building my product (using Tycho) for 4.2 'Themes' list is empty in 'Preferences' - https://i.sstatic.net/JmTqH.png. However when I view in Eclipse 4.2 IDE list is there and all the checkboxes are present. Any idea why this happens?
There are bundles missing which contribute the themes. Find out which ones they are and add them to your product.
