Javascript error when changing the logo of a color theme on IE8

Steps to reproduce:

• Hover over "Wiki" and click on "Administer Wiki"
• Click on "Presentation"
• Click on "Manage Color Themes"
• Click on the default theme
• Click "Edit"
• Hover over the XWiki logo and click on the pallette
• Write another logo name in the logo field

You are able to change the logo, but you'll get an error when you modify that field. I've attached a screenshot.