Steps to reproduce:

1. Go to a page with a really long article title, on the mobile site, with Advanced Mobile Contributions enabled, on a smartphone or a narrow screen.
2. Click 'Categories'
3. Click 'Add to category'
4. Click 'Search categories'
5. Select a category
6. The top says 'Add <extremely long article name> to new cate...
7. Try to find the blue "Publish" button.