See attached screenshot. 'Hide/Show Columns' dialog shows unnecessary menu on the top and the bottom.
In order to fix, it is necessary to set portal.pda.bypass.sakai.gradebook.tool=hideshowcolumns$ in sakai.properties.
Steps to reproduce:
1. Log in from a mobile device.
2. Select a site.
3. Select Gradebook.
4. Select 'All Grades' link.
5. Select 'Hide/Show Columns' link. Then, the dialog is shown.